The human male never passes on the gene for red green colour blindness to his son . How is it so ?

The genes responsible for colour vision are present in X chromosomes only. If some of these genes are mutated or damaged or not expressed, colour blindness occur. We know that human males are XY and females are XX. Female always produce X chromosomes while male produce both X and Y chromosomes. Whenever male passes X chromosome, the child is female. A son is born only when father passes Y chromosome and it is known that the genes responsible for colour blindness are present in X chromosome. Therefore, a father can never pass genes responsible for colour blindness to his son.