A normal-visioned man whose father was colour-blind, marries a woman whose father was also colour-blind. They have their first child as a daughter. What are the chances that this child would be colour-blind?

1. Man: Normal visioned ($XY$). His father's condition doesn't matter because a son inherits only the $Y$ chromosome from his father.2. Woman: Her father was colour-blind ($X^{c}Y$), so she must be a carrier ($X^{c}X$).3. Cross: $XY\times X^{c}X$ Possible Genotypes for Daughters: $XX$ (Normal), $X^{c}X$ (Carrier).Since both possible daughter genotypes result in normal vision (phenotypically), the chance of the daughter being colour-blind is zero.