Can Dogs see Colors?

The question if dogs are colorblind, specifically red-green colorblind or if dogs only see shades of gray is raised among dog owners quite often. Even on the internet the question concerning dog vision is discussed controversial. But there is a simple answer to that question which I would like to share with you supported by some scientific resources.

Actually there are two distinct questions which I would like to ask, answer and set in relation hereafter:

  1. Can dogs see colors? — Answer: Yes
  2. Are dogs colorblind? — Answer: Yes

Let me explain this two answers to you a bit more in detail.

Dogs can see colors
Dogs not only see in shades of gray but also can see distinct colors contrary to what most people belief. About one hundred years ago some scientific tests were made to find out more about the color vision of dogs. But these tests weren’t that scientific as they thought and the researchers concluded only that color vision doesn’t play a part in the daily life of a dog.

Only about 90 years later distinct researches have shown that dogs can perceive colors. Neitz, Geist and Jacobs researched in 1989 the color vision of domestic dogs and found the following facts:

  1. Dogs have two different color receptors in their eyes and therefore are dichromats.
  2. One color receptor peaks at the blue-violet range, the other at the yellow-green range.
  3. Conclusion: Dogs are green-blind which is one form of red-green color blindness also called deuteranopia.

This results were support by later researches of Jacobs with colleagues in 1993 and Miller and Murphy in 1995.

Dogs are colorblind
This directly leads us to the second question concerning the color blindness of dogs. Colorblind doesn’t relate to not see any colors but describes the fact that you can’t see the same color range as somebody with normal vision. Because of that any kind of color vision deficiency is called color blindness. Therefore dogs are colorblind because of their dichromatic color vision.

Colors dogs can’t distinguish
Actually the color spectrum made up of wavelengths of light is the same to all of us. Only the perception of those colors can be quite different. As dogs only have two different color receptors in their eyes they have problems to distinguish certain colors:

  • Red — Orange — Green
  • Greenish Blue — Gray
  • Different shades of Purple

The list is not completed and there are a lot of different shades which can’t be differentiated if you are colorblind. And the conclusion is dogs can see colors but are at the same time colorblind.

More facts on the vision of dogs can be found in the book Handbook of Applied Dog Behavior and Training, Vol. 1: Adaptation and Learning by Steven R. Lindsay.

Meet with other Colorblind Women

During the last days I was contacted by colorblind women seeking other colorblind women to share thoughts, ask questions and just to talk. I was looking for a way to make it possible to meet and discuss. Finally I set up an own forum about color blindness here at Colblindor, where everybody can join and talk about color blindness viewed through colorblind eyes.

Color blindness in women is very rare. Only about 0.5% of all women have some kind of color vision deficiency and often this isn’t even recognized. Most people think color blindness is only man’s business – but that is wrong.

Because the biology behind red-green color blindness tells us, that much more men are colorblind (approximately 8%) this doesn’t mean that women can not be colorblind. Specially very uncommon cases like tritanopia (blue-yellow color blindness) and monochromacy (complete color blindness) are equally distributed among men and women.

Update: Because the forum was mostly a huge spam trap I removed it again. Sorry if any inconveniences arise through this.

One Year Anniversary of Colblindor

It was exactly one year ago when I started blogging in the name of Colblindor. Well it wasn’t really the start of my blogging career. I started a few weeks earlier writing about everything and nothing. But soon I realized that this wasn’t my way in blogging and at this point Colblindor was born.

First of all I was looking around for a topic to write about. A topic I new something about, I had a personal connection and something that wasn’t covered by a lot of others. And the search of a topic ended up at color blindness.

The first time was tough. I had to do a lot of research, didn’t know how to write blog posts and was kneeling right into it, posting around once a day. It was a good time where I learned a lot about color blindness, blogging and a lot more. A lot of tests with designs, plugins, communities and a lot more followed which filled my everyday life besides job and family.

After a few month I was quite happy with what I achieved but an event let me stop writing for several month. We bought a house. This took up a lot of time, effort and work.

But after a few months of hard work I started again with blogging. Why? Because I missed it, I needed again a change and I just wanted to come back. My comeback wasn’t that strong. I posted only a few times a month and slowly kept it going.

Again a few months later visitor numbers started to increase and I started even to earn some money through advertisement. So I decided to give it another try and start posting at least two times a week. It’s not that easy for me because there is a lot to do besides writing about color blindness: job, family, renovating our house, sport and so on.

And that’s where I am at the moment and as a reward I can see the traffic counts increase.

Some facts as of 21st February 2007:

  • 132 posts
  • 141 comments (with over 35’000 rejected by Akismet)
  • Average of 170 unique visitors a day
  • Average of 378 pageviews a day
  • 36 RSS subscriptions
  • Total earnings of 92$

Most popular articles:

BTW I constructed the name Colblindor while looking for a unique naming for my weblog. I just played around with the words color and blind. And I am still quite happy with the brand I created. As happy as I hopefully soon will switch to color-blindness.com.

Ishihara Plates Color Blindness Test in a Leaflet

Unfortunately those leaflets are not available anymore. But you can find the whole set of 38 Ishihara plates in my article: Ishihara’s Test for Colour Deficiency: 38 Plates Edition.


Just recently I found this new Web 2.0 application where you can produce your own leaflets. A leaflet is a miniature web site which can be created online and distributed through an URL or an embedding link.

I thought this could be a great way to show the 35 Ishihara plates to test your color blindness. All plates show a big circle consisting of many little colorful circles. Because the circles differ in color and brightness it can get really tough for a colorblind person to see the shown numbers or traces.

If you take the following color blindness test be aware that those pictures were scanned and are now reproduced by your display. This can alter the colors. Because a color blindness test relies solely on correct color reproduction you shouldn’t take the results for granted. If you really want to check your color blindness you should see your local doctor.

Could you perform as you expected? Or did the plates show that you really are red-green colorblind? I hope you could spot at least the number in the first and the trace in the last plate, otherwise you may have a real severe color vision problem…

Windows Vista Upgrade List

Windows Vista Upgrade List

Windows Vista Upgrade List

Yesterday I bought a new laptop. What I definitely wanted to have included in the package I bought was the new operating system form Microsoft: Windows Vista.

And just after I made the deal I found this upgrade list for Windows Vista in a newsjournal of a local book and software seller. Not that I want to buy an upgrade. But out of actuality reasons I had a look at it — and was very much confused.

The scanning of the image and also each individual computer display doesn’t show the exact same colors as they are printed in the journal. But when I looked at the journal I couldn’t make a difference at all. Even when I looked really really close, my color blindness forbid me to distinguish the two different colored circles.

Don’t they have one person working at this magazine who is also colorblind? This can’t be true that they choose a shade of green and a shade of red which are so close together. I thought the term red-green color blindness made it’s way around…

I will write them a short notice and see what they think about it. Luky me, I already ordered the windows vista of my choice.

Terminology of Color Blindness

If you scratch under the surface of color blindness you sooner or later will come across many different terms related to color blindness which are not really self-explanatory. To get a better understanding of the terminology of color blindness I try to lift the curtain at least a bit.

General terms
Color blindness – a term which is misleading – is also known as color vision deficiency or daltonism. Color vision deficiency is not very well known but describes the phenomenon more precisely. Daltonism is named after the first scientist who wrote about color blindness. More details about these terms can be read in my recent article about Color Blindness is not ‘Color Blindness’.

Types of color blindness
There are four different types of color blindness which can be distinguished. This relates to the fact, that humans have three different color receptors in the eye (red, green and blue sensitive cones) and each of them can either be absent or working not properly. The fourth type describes the real color blindness.

  • Protan: The first type of color blindness relates to the red cones. Protanopia describes the fact that these cones are missing at all whereas protanomaly describes a displacement of them. Better terms would be red-blind as a synonym for protanopic and red-weak as a synonym for protanomalous.
  • Deutan: This term describes all green cone related conditions. If the green cones are missing it is called deuteranopia and a displacement is called deuteranomaly. Again some better terms to describe theses deficiencies in common speech would be green-blind (deuteranopic) and green-weak (deuteranomalous).
  • Tritan: Blue cone deficiencies are either called tritanopia if the blue sensitive cones are absent or tritanomaly if they are displaced. According to red and green cone deficiencies tritanopic is also called blue-blind and tritanomalous blue-weak.
  • Achromatopsia: This is the real color blindness. An other term for achromatopsia is rod monochromacy, because the cones are almost completely missing and since cones see colors whereas rods only see lightness this relates to complete color blindness and even a strong sensitiveness to bright light.

The very well known term red-green color blindness is an umbrella term including protan and deutan vision deficiencies. More information can be found in my earlier articles about protanopia and tritanopia.

Types of color vision
Color vision can be different in animals than in humans. Some animals have more types of cone cells and some have less. Even humans can not only have less but also more than three color receptors (see the article about tetrachromats).

  • Tetrachromatism: Four different color receptors. This is very unusual in humans but can be found in some animals.
  • Trichromatism: Three different color receptors related to red, green and blue. This is what we call normal vision.
  • Anomalous trichromatism: Three different color receptors whereas one of them is more or less good working. This relates to protanomaly, deuteranomaly and tritanomaly.
  • Dichromatism: Two different color receptors which describes the three different types of color blindness protanopia, deuteranopia and tritanopia.
  • Monochromatism: Either no color receptors at all or only one type of color receptors. This is also called rod monochromacy or achromatopsia.

These most commonly used terms in color blindness are not really common speech and can hardly be remembered. I like the terms red-blind, red-weak, green-blind, green-weak, blue-blind and blue-weak definitely the most. But unfortunately they are not very well known.

At least the term red-green color blindness is very accurate, describes the most common form of color vision deficiency and is even very well known.

New Outfit

And again. I changed the design of Colblindor again. Why? Because I already didn’t like the old one anymore and it was cluttered and not really expandable.

This time I switched to a theme, which I didn’t have to change much. Just simple and nice. I hope you like it too. Maybe I am a bit change addicted and should better put some more effort into good content than changing the parameters of this blog all the time. But that’s the way I work…

By the way the theme is called NonZero and was released by Headsetoptions.

Colorblind at the Traffic Light

Traffic Light

Traffic Light by Rivertay

I have a drivers license for more than ten years now. When I applied for it I didn’t had to take a color blindness test. This is maybe the reason why I have one…

The question most people think about when they hear, that someone who is colorblind and does have a drivers license is: “How do you know when to stop at the traffic light?” And they don’t stop thinking here but start to find a reason themselves.

People conclude that if you are colorblind you know, red is on top, green at the bottom and that’s the way colorblind people find their way through the traffic jungle. But that’s wrong.

Why is it wrong?

  • The association between top and stop, bottom and go is to weak.
  • The connection for deciding what to do is not fast enough.
  • The thought needs to many steps. Light – top – stop is one step to much.

So what do you do if you are colorblind?

Colorblind doesn’t mean you can’t see colors at all. You can see colors, differences in hue, saturation and lightness. Maybe not as good as with normal vision, but you definitely have a broader vision than just black, white and gray. And because of that, people suffering from color blindness do see different colors at the traffic light. Some more differences, some less and maybe not the same difference in color as people with normal vision. But all you have to learn is which color you see relates to which reaction.

If you are colorblind you know this color means stop and that color means go. You don’t know the name of the color. You maybe can’t relate the colors you see at the traffic light with other colors in the nature. You even may give them other names. But you will always know the difference because you can see a difference.

Traffic Light

Traffic Light by i_yudai

If you are not affected by color blindness I suppose all this is hard to imagine. Have a look at some pics and help your imagination. Some pics are about Walk – Don’t Walk pedestrian lights, modulated to show different color vision deficiencies.

By the way, there are many traffic lights not only from top (red) to bottom (green) but from left (red) to right (green). If you would just remember the sides, you definitely would mix them up all the time.

Color Blindness Test based on Confusion Lines of the CIE 1931 Color Space

This is the third and last part of a series, where we have a closer look at a color blindness test which is based on the confusion lines of the CIE 1931 color space. In the first part I introduced the CIE 1931 Color Space and the second part was looking a bit deeper into the theory of Confusion Lines.

Most tests which check for color blindness are based in some way on confusion lines. But I would like to focus your attention on this test which is regenerated for every single trial based only on confusion lines.

The author of the test describes the design for his color vision test as follows:

  1. For each color vision deficiency (protanopia, deuteranopia or tritanopia) test, five confusion lines are selected randomly. Three points on each confusion line that can be distinguished by the normal observer are chosen.
  2. For each test, a confusion line is selected randomly. A point is selected randomly among the set of three. It is displayed in the upper test panel at a random luminance in the form of random dots. The three points are displayed in the lower three panels at a random luminance and also in the form of random dots.
  3. The subject is asked to check one of the lower panels which color matches that of the test panel.
Color Blindness Test - Example Screen

Color Blindness Test – Example Screen

As I described in part two of this series, colorblind people can distinguish only a handful of wavelengths of the color spectrum. Compared to normal vision it is around 10% to 20%. But if you are affected by color blindness you automatically start to interpret a difference in lightness as a different color. This makes you think to see more colors than you actually can distinguish.

If we look at the description of this color blindness test this is exactly the point of it. It plays with the lightness and adjusts the three choices to the same lightness, which makes it really hard to get the match if you are colorblind.

I took the test. It showed me cruelly – cruelly again, that I am very much colorblind. But let us have a look at my results. I took each color blindness test three times and completed each time 50 decisions. What is amazing to me is, that in all three tests the results didn’t differ a lot, or better said almost none. Let me start with the best results:

My Tritanopia test results

Run Correct Wrong Correct%
1 47 3 94%
2 49 1 98%
3 47 3 94%

Most of the time I could tell a difference between the three choices. But still I had to guess every single time. I suppose the problem is that I can’t name the colors I see, I just see different colors and nothing more. (→ Tritanopia Test)

My Deuteranopia test results

Run Correct Wrong Correct%
1 31 19 62%
2 30 20 60%
3 35 15 70%

The results are much worse compared to the first test. Although I still could distinguish usually one of the three colors from the other two it was more of a guessing game than really knowing anything. (→ Deuteranopia Test)

My Protanopia test results

Run Correct Wrong Correct%
1 26 24 52%
2 24 26 48%
3 25 25 50%

This color blindness test was pure guessing. I couldn’t tell a color from the other and I am very much amazed of the results. The lightness adjustment made it impossible to me to match them correctly. (→ Protanopia Test)

The results of this color blindness test in three parts approve the outcomes of other tests. I am protanopic or at least affected by a very strong protanomaly and as the doctor would say: “You are completely colorblind.”

More information about the color blindness test based on confusion lines and the online tests itself can be found at the Color Vision page of biyee.

This was the third and last part of this series. The other parts can be found at
Part 1: CIE 1931 Color Space
Part 2: Confusion Lines