If a colorblind woman marries a colorblind man, the chances of any daughter being of normal vision is

Color blindness is an X-linked recessive disorder. The woman who is colorblind must be homozygous for the recessive allele. If she marries a colorblind man, then 50% of the offspring will be colorblind, and 50% will have normal vision. Out of the normal offsprings, a half population would be a female, and half would be male. So, there are 25% chances that the daughter will have a normal vision.