Often people think that if you are suffering from red-green color blindness you can not distinguish red from green at all. But they are wrong.
The term red-green color blindness isn’t accurate and doesn’t describe the actual color vision deficiency correctly. If you have a look at the confusion lines of the CIE 1931 color space you will see, that there are many different lines in the color space which connect undistinguishable colors to a colorblind person. Therefore a red-green color vision deficiency makes you colorblind to many more colors than just red and green.
On the other side it depends strongly on the brightness and saturation of colors to make them hard to distinguish if you are colorblind. Colorblind people often develop some sort of color intuition which is based not only on the hue but also on the brightness of the color they see. Something which is hard to imagine if you have normal color vision.
For example some shades of red are close to green, others close to brown and again others are even close to black. The following list shows a few examples of colors which look close to each other and can’t be distinguished easily if you are suffering from red-green color blindness:
- yellow — bright-green
- orange — grass-green
- apple-red — leave-green
- dark-green — brown
- blue-green — gray — purple
- dark blue — violet
As a conclusion you can say that some reds and some greens are very well distinguishable. It depends very much on the brightness and the saturation of each color to make them undistinguishable for a red-green colorblind person.