Human female is referred to as carrier of colour blindness.

Explanation

Human female is referred to as carrier of colour blindness because of the following reasons :
(1) Unlike the males who are heterogametic the females are homogametic.
(2) A female having one recessive gene on X chromosome is a carrier female, while a female possessing both recessive genes on both the X chromosomes will be colour blind which is very rare.
(3) If a carrier woman marries a normal man, they will have half of their daughters having normal vision and the remaining half will be carriers of colour blindness.
(4) Her son becomes colour blind due to X-linked gene transmitted through her. Hence, human female is referred to as carrier of colour blindness.