A couple having normal vision gave birth to a son having colour blindness(sex linked disease).On investigation it was discovered that the gene was inherited from the child's grandparents(mother side).Justify showing a proper cross.

Grandparents have genotype female-X^hX  and male- X^hY
The mother may have genotype X^hX  and X^hX^h but she has normal vision so she will have X^hX but she is a carrier therefore to their son  its infected X gene and fathers Y gene is transferred do he is colorblind.The father genotype is XY because he has normal vision

Therefore the genotype of the son will be X^hY which is he is a colorblind