-this refers to any condition in which colours cannot be distinguished
-the most colour formed is the red-green colour blindness in which the person cannot distinguish between red and colour from green colour
-it is a sex linked character caused by a recessive allele carried on the X-chromosome
-the pattern of inheritance is similar to that of haemophilia
-females are normally carriers and they transmit the trait to their sons
-it is also caused by mutation
-5 genotypes are present
-XCX, XX, XCY, XY, XCXC