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Color blindness is typically a genetic condition, and it is much more common in men than in women. Approximately one in 12 men has at least some color perception problems. Less common, acquired deficiencies stem from injury, disease, or the aging process. Also, although not called "color blindness," when people age, their corneas typically turn yellowish, severely hampering their ability to see violet and blue colors.
How do things look?
Many people think anyone labeled as "colorblind" only sees black and white -- like watching a black and white movie or television. This is a big misconception and not true. It is extremely rare to be totally color blind (monochromasy - complete absence of any color sensation). There are many different types and degrees of colorblindness - more correctly called color deficiencies.
People with normal cones and light sensitive pigment (trichromasy) are able to see all the different colors and subtle mixtures of them by using cones sensitive to one of three wavelength of light - red, green, and blue. A mild color deficiency is present when one or more of the three cones light sensitive pigments are not quite right and their peak sensitivity is shifted (anomalous trichromasy - includes protanomaly and deuteranomaly).
Summary
There are several different kinds and degrees of color vision deficiencies. Protanomalous or deuteranomalous individuals can usually pass as a normal observer in everyday activities. They may make occasional errors in color names, or may encounter difficulties in discriminating small differences in colors, but usually they do not perform very differently from the normal except on color vision tests.
The protanope and deuteranope, on the other hand, can be severely color deficient. The real problem, as a protanope or deuteranope may see it, is there are far too many hue names (color names) used by most people without any obvious basis for using one instead of another. Why call something "orange" when it doesn't look different in any way from something else called green, tan, beige, or any of several other color names?
