When you look at this circle what number do you see? If you don't see a 6 then you are color blind. People with color blindness generally have trouble seeing reds, greens, blues, or a mixture of the of the three. Most commonly is seeing red and green as the same color. 1 in 12 men and 1 in 20 women are born with color blindness, most often caused by genetics and usually present at birth.
Color blindness is caused by mutations of the X chromosome, leading males to be more likely to receive it, they only have one X chromosome and women have 2. There are many forms of color blindness, including some that are temporary (caused by migraines) and also having color blindness only in part of ones view.
Before doing any research I had no idea how many people were actually effected by color blindness and it leads to an interesting part about art. Graphic Designers, while color plays a large part of what they do, they cant solely rely on it. If you are trying to reach as broad an audience as possible you need to be conscious of of the colors you are using. You cant make a point by just having contrasting color, because it may not reach as broad of an audience.
http://en.wikipedia.org/wiki/Color_blindness
http://www.colormatters.com/v_colorblind.html
