What about “color blindness?”

May 24th, 2010 | Posted by Stone

“Color blindness,” or more formally, color vision deficiencies (CVD) affect roughly 10% of the population, mostly men.  Few people are truly blind to color; most simply have some degree of weakness perceiving certain parts of the spectrum.  People with CVD often compensate by being more sensitive to differences in luminance, texture, and position.

Predicting the effect of CVD is difficult because it affects color vision very early in the perceptual processing. In the eye, colored light is converted to three neural stimuli by the cones, specialized cells that live in the retina. Humans have three different cones, which are sensitive to different, overlapping ranges of wavelengths. Protan, deutran and tritan refer to people with anomalies in the cones most sensitive to long, medium and short wavelengths respectively.

Roughly speaking, protans and deutrans both have difficulty discriminating red from green, but tritans have difficulty discriminating between blue-purple and yellow. But, the reality is much more complex.

Many people with CVD can see colors when they are very bright and saturated, but not when the hues are more subtle, as in pastels or “earth tones.” A common problem for protans, who have difficulty seeing red light, is distinguishing brown from gray.  Deutrans have difficulty distinguishing green from amber, especially on displays, where the green is very yellowish. Both protans and deutrans have difficulty distinguishing blue from purple (which is blue plus red).

Fortunately, there are tools for simulating color deficient vision, such as Vischeck. The simulation models extreme cases of CVD where one cone is completely missing. However, any design that is legible in this extreme case should also work for people with less severe CVD.

Recommended reading: Colblindor, Color blindness viewed through Colorblind Eyes

  1. color blindness
    Aug 8th, 2010 at 22:28
    Reply | Quote | #1

    thanks for giving such a deep knowledge about color blindness type like protan ,deutran and tritan .