Most colour blind people are able to see as clearly as other  people. They are unable to see fully red-green or blue light.It is sex linked genetic disorder, affects male more than female, in male 1 out of 12 male is colour blind & in female 1out of 200 females is colour blind. Colour blindness is not a blindness but a deficiency in the way you see colour.  Currently no treatment for inherited colour  blindness, vision of most colour blind people is  usually normal in all other respects.Face book is blue because it's founder Mark-zuckerberg suffers from red green colour blindness.