Red-green color blindness is an X-linked trait.
Explanation:
A red-green color blindness is a hereditary disease which occurs with inheritance of recessive X linked chromosomes, which depicts that the gene or allele causing this defect is presents on the X chromosome.
Since males can express the recessive gene with one copy of the X chromosomes, this defect is more common among men than women.
So even if a grandfather has this defect, this may get inherited by his grandson, while his mother might just be a carrier.
This is the reason why the baby boy inherited the red-green blindness from his father.
