A property professional with nearly 20 years experience of estate agency in Suffolk and North Essex. During that time I have carried out market appraisals on over 5000 residential properties and have helped over 1500 people successfully sell their home.
Therefore, a son from a color-blind mother (who receives the trait from his mother on the X-chromosome) will always be color-blind, regardless of the state of the father (who can only give his son a Y-chromosome).
XnY one color blind boy. 1  Probability of having a color blind daughter is (1/2 x 1/2) or 1/4 or 25% (0.25) This is because both sex and colorblindness are involved in the solution.  The probability that their first son is color blind is 50% (0.50). In this question only males are part of the solution.