14.Una mujer del grupo sanguíneo A tiene un hijo del grupo B. Se duda de la paternidad entre dos varones, uno del grupo AB cuyo padre era del grupo B, y otro del grupo O cuyo padre era del grupo B. Resolver la cuestión.

If the child is B, and the mother is A: then the possible genotype of the father should be blood group AB, with genotype AB, co-dominant while the possible genotype of the mother should be AA. AO. Consequently, The child ‘s blood group should be A, AB, B. Thus the man who belongs to blood group AB is the father.

The man of the blood group O, cannot be the father, since his blood group is O  (universal donor), genotype is  OO, then the possible blood type of the child are  either A or O, with the woman(AA, AO), but not AB that the child has.

This is because the possible genotype of the O group  man can only be OO and that of that woman AO, AA, so no chance of having a child of B group.

Hence AB father, fathered the child.  

Explanation:

the father in the first generation probably had the recessive colorblind trait in his x chromosome. if he and his wife both had the colorblind trait, even if she had 1 recessive and 1 dominant, then that trait would be passed on to their kids.

(since you didn't attach the family tree this is just an assumption)