Color blindness also known as color vision deficiency (CVD). It is a deficiency in distinguishing between different colors. It occurs when light-sensitive tissue in the back of the eye—the retina–fails to properly respond to variations in wavelengths of light, which enable people to see different colors.
Design elements and techniques that improve color accessibility for color blind users are generally considered to be good design practices.While you might think that your website's aesthetic appeal might suffer if you design for accessibility, that's certainly not the case.
It is remarkable that approximately 8% of all Caucasian males and 0.5% of females experience problems with some forms of color deficiency,and it means that 1 of 20 users may not be able to see your website in its full beauty. For these viewers the text may be fuzzy and images may be unrecognizable.
Our eyes need 3 types of cone cells that will help us recognize all the colors, which are the long (L), medium (M) and short (S) cones. Each of them helps us determine a different spectrum of colors depending on their wavelengths.
Missing or dysfunctionning L cones, which lowers sensitivity to Red hues.
Missing or dysfunctioning M cones, which lowers sensitivity to Green hues.
Missing or dysfunctionning S cones, which lowers sensitivity to Blue hues.
2 or 3 types of the cones are either missing or dysfunctioning, which can completely lower sensitivity to all hues of colors. People with monochromacy see the world in shades of gray.