why is color blindness more frequent in boys?

The term 'colour blindness' is misleading. People who can't see all colours can still see things (other than colour) as clearly as people who are not colour blind. The term means that a person can't see some colours, or sees them differently from other people. Very few people who are colour blind are blind to all colours. The usual colours that people have difficulty with are greens, yellows, oranges and reds. Colour blindness is inherited, affecting more boys than girls. Out of 20 boys, it is likely that one or two will have a colour vision problem. Colour blindness is inherited. Red, green colour blindness is usually inherited. It occurs in about 8 per cent of males and only about 0.4 per cent of females. This is because the genes that lead to red–green colour blindness are on the X chromosome. Males have only one X chromosome and females have two. The son of a woman who carries the gene has a 50 per cent chance of being colour blind. The mother is not herself colour blind because the gene is recessive. That means that its effect is suppressed by her matching dominant normal gene. A daughter will not normally be colour blind, unless her mother is a carrier and her father is colour blind. Only five per cent of people who are colour blind have blue colour blindness. This is equal in males and females, because the genes for it are located on a different chromosome. However, colour blindness is not always inherited. It can also be due to a change in the chromosome during development.