bp's science: color blindness (v.1)

I was amazed to find out, depending on the source, that 10 to 20 percent of males are color blind. I guess I shouldn't be surprised since I know a few color blind fellows myself. But the term color blindness does not refer to just not being able to see color. Color blindness comes in many shapes and sizes, ranging from total color blindness to color deficiency. In fact, of the fellows I know who are color blind, two different types of color blindness are exhibited. Color blindness is usually inherited but can be acquired if an eye injury occurs.

Taking it down to the basics, there are three types of color blindness.

Monochromacy: individual can not see any color but can only distinguish brightness
Dichromacy: individual has a hard time seeing colors like red or green; to them red is very dark and/or green is white, in more specific terms the individual can only see colors using two spectra of light (normal vision uses three lights)
Anomalous Trichomat: individual has a hard time distinguishing between different colors of red or different colors of green, for instance, olive green and tan look like the same color, in more scientific terms the individual can see colors using three spectra of light like normal vision but they require more of a specific light than normal to match the spectra

For the fun of it, here are some color blind Ishihara tests. What numbers do you see?

Answers:

Left column - Right column
25 - 29
45 - 56
6 - 8

This is where I should mention that of the color blind fellows I know, one is a dichromat and the other an anomalous trichomat. The dichromat can only see the number 25 (and barely, if not at all, the 56), while the trichomat can see four of the six numbers, excluding 45 and 6.

Now my color blind friends claim that being color blind puts them at an advantage in other areas of sight, for instance, they can see better at night. I totally believe it and think they deserve it. Obviously, I was happy to find in my research that the U.S. Army found that "color blind people could spot 'camouflage' colors that fooled those with normal color vision."

Read more about color blindness here and here.