Two weeks ago I wrote an article about Protanope Tools and how you can translate diagrams to make them more readable for colorblind people. This time we have closer look at the algorithms behind the two color translations.

To understand the how and why of the two color translations we first have look at the RGB color system. The acronym RGB encodes the colors Red, Green and Blue and is used on computer system color displays to—well— display colors.

Concerning red-green color blindness the first two channels (Red/Green) are sometimes not of great help. These two channels are encoding the color axis which gives a red-green colorblind person the most problems in distinguishing different shades. Therefore we are looking for a simple way to transform those two channels.

Red-Green Color Blindness Color Translation Algorithms

• Red-Green to Blue-Yellow Translation
  
  • R -> B
  • G -> G
  • G -> R

• Red-Green to Green-Magenta Translation
  
  • R -> R
  • G -> G
  • R -> B

The two translation formulas are held very simple but not less effective. They have only one major flaw: the blue channel is completely thrown out and in both cases replaced by the red channel. So you lose a third of the information in the image, all the blue information, except that if you are red-green colorblind you gain a lot of information that was previously lost in the red and green channels.

As Peter, the owner of Protanope Tools, puts it:

I say this is a strength because the simplicity makes it easy to understand exactly what’s happening, so if you know you’re going to lose all the blue information at least that won’t take you by surprise.

Thanks Peter for the information about your simple color translation algorithms you shared with us.

There are many online tools which help you to choose an appropriate color scheme based on color theory. ColorJack is one of them. But not just anyone when you take color blindness into account. The creator put quite some effort into the tool to help you understand how a colorblind persons will perceive your chosen color scheme.

The most popular part of ColorJack is the Sphere application. Before I describe you all settings in detail and special adjustments concerning color blindness try it out yourself.

Besides all the settings for choosing your spectral colors according to different color theories and the possibility to set the base color spectrum you have the choice to choose between several different color vision deficiencies.

• Dichromacy: Protanopia, Deuteranopia and Tritanopia.
• Anomalous Trichromacy: Protanomaly, Deuteranomaly and Tritanomaly.
• Monochromacy: Rod Monochromacy and Blue Cone Monochromacy.

The naming needs some further explanation because the labels in the Sphere tool are not well chosen. As for dichromacy which describes the circumstance, that a person has one type of color receptors missing, the correct names end with -opia and not as labeled in the tool with -opy.

The wordings Achromatopy and Achromatomaly used in the tool of ColorJack are also wrong. The correct names are either Rod Monochromacy or Achromatopsia for complete color blindness (absence of all color receptors) and on the other side, if you have only blue color receptors this is called Blue Cone Monochromacy.

Nevertheless the ColorJack Sphere application is a great tool to provide you some good information when you want to check your color scheme to work with any type of color blindness. It does not only show how your colors are perceived by somebody with a color vision deficiency but also shows the according color values. This gives you a hint on how color vision is different if you suffer from color blindness.

It can be really annoying if you find some descriptive graphics or a nice diagram and you can’t decipher it because it is color coded. Even if you are suffering from red-green color blindness — which is the most common form of color vision deficiencies — you aren’t spared to come across such diagrams.

Have a look at the following diagram of the climate classification. If you are red-green colorblind it can be a big problem to distinguish Tropical from Cold and also Dry from Temperate zones. In the first case it doesn’t really matter because the different zones are far apart form each other. The latter case is worse.

In such cases Protanope Tools comes in very handy. With this little online tool you can change the color spectrum and make those undistinguishable parts of color coded diagrams visible. Protanope Tools is made for red-green colorblind persons and offers two different possibilities:

1. Shift from red-green to blue-yellow.
2. Shift from red-green to green-magenta.

Have a look at the following two diagrams which were created with Protanope Tools based on the above image. The colors change dramatically. In both cases the climate zones Dry and Temperate are clearly distinguishable. Even though Cold looks almost the same as Temperate and also Tropical and Dry look almost the same if you suffer from a strong red-green color blindness.

Protanope Tools offers the possibility to color translate any image. You can just drag the two bookmarklets below to your browser bookmarks and this way you always have the two direct color translations ready whenever you come across a colorful diagram.

• Color Translation 1: Red-Green to Blue-Yellow
• Color Translation 2: Red-Green to Green-Magenta

The best case when you colorize your own diagrams is and will always be the one, where nobody needs a separate tool to understand your message. Be aware of color blindness when you color code your own graphics and for every other case Protanope Tools will help you out.

Update: To get a better understanding of what goes on behind the scenes of these color translations, read the article on Simple Color Translation Algorithms, which reveals the two algorithms used above.