Color blindness is the inability to distinguish particular colors. It
is generally an inherited trait, but can result from a chemical imbalance or eye
There are three primary colors. They are red, blue, and yellow. All
other colors are the results of different combinations of primary colors.
Special visual cells, called cones, are respon-sible for our ability to see
color. People with normal vision have three different types of cones, each
responsible for a different primary color.
The absence of particular cones causes the absence of particular colors.
This can be one cause of color blindness. There are four types of color
blindness. The rarest forms are mono-chromatism and a-typical monochromatism.
People with monochromatic vision, or total color blindness, has no cones at all.
As a result, they have no ability to see colors, and no hue discrimi-nation
whatsoever. Monochromatic vision is very similar to watching a black and white
Somebody with a-typical monochromatic vision has just one type of cone,
and can see just one color, and various shades of that color. This form is even
rarer than the "typical" monochro-matism.
Another, more common, form of color blindness is called dichromatism.
People with di-chromatic vision tend to confuse red, green, and gray, but can
easily distinguish blue and yellow. Some cannot even see the longest wavelengths
of light -- the red end. Though it is rare, others cannot see the short
wavelengths, near the violet end. These people tend to confuse blue, yellow,
and gray, but not red and green.
Normal vision is called trichromatism. Most color blind people have a
version of trichro-matism called anomalous trichromatism. People with this
condition can see the same colors as people with normal vision, but not as well.
For example, many people with this common form of color blindness are "green-
weak". This means, they see green, but to see the same color normal people see
when green and yellow is mixed, more green must be added. "Green-weak" and
"red-weak" are the most prevalent forms of anomalous trichromatism. The...