pedigree chart help me

Red-green colour blindness is an x-linked recessive trait.

Hence, a male must have the mutant copy of the gene to be red-green colour blind, and the female must have 2 copies of the mutant gene to be red-green colour blind. Knowing this, we can fill out the pedigree chart.

Here are the genotypes:

I-1: Yx (affected)
I-2: Xx (1. not affected so has one dominant normal allele. 2. heterozygous/carrier because one female progeny and both male progeny are affected.)

II-1: YX (not affected)
II-2,4,6: Xx (1. not affected so has one dominant normal allele from mother. 2.heterozygous/carrier because inherited one recessive mutant allele from father.)
II-3,5: Yx (affected so inherited one recessive mutant allele from mother.)
II-7: xx (affected so inherited one copy of recessive mutant allele from each parent.)
II-8: YX (not affected)

III-1: Xx (not affected so inherited one copy of dominant normal X allele from father.)

So now, let's answer the questions:

a. I-I is Yx. The other three are Xx

b. II-1 crossed with II-2 = YX crossed with Xx. (So for a male progeny, we only have the following two possibilities: YX, Yx.
For the son to be affected, he must inherit the x mutant allele from the mother and the probability of that is 50%.

c. II-7 crossed with II-8 = xx crossed with YX. (So for a male progeny, we only have the following possibility: Yx)
Hence, there is a 100% chance that their son will be affected.

Hope this helps!