An acentric fragment is one result of crossing-over between a normal chromosome and a chromosome that has undergone what kind of mutation?

paracentric inversion

Explanation:

A paracentric inversion happens as a result of a portion of one chromosome , or a packet of genetic information, which is flipped such that there are changes in the order of genetic information. Every of the chromosome has a part that is near the middle which is referred to as a centromere. Paracentric inversions do not include the involvement of the centromere of a chromosome.

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)