Answer:

Red-green colorblindness is an X-linked monogenic recessive trait.

Because it’s a recessive trait and the mother exhibits the phenotype - i.e., she is more than just a carrier for the trait - we know she must be homozygous for the trait, carrying two copies of the colourblind allele. The father only has one X chromosome, so although he carries only one colourblind allele, it’s the only allele he has, so he exhibits the colourblind phenotype.

In this cross, there are only colourblind alleles, so necessarily all of the children will have the colourblind phenotype. All of the male children will have a single allele, and all of the female children will be homozygous for the colourblind allele.

The nomenclature for X-linked traits sometimes varies a little from the usual AA/Aa/aa, because we need to keep track of the X and Y chromosomes in male and female individuals. If this is a homework question I’d check what you’ve been taught, but I prefer to use X and Y with a superscript to indicate the allele (not least because there are ascii characters for most of the lower case letters, making it easier to type); “+” is used for the dominant allele and a lowercase letter for the recessive allele, which would be X⁺ for normal vision allele and Xᶜ for the colourblind allele. Again, in this case there are only Xᶜ alleles, but for the father you would write XᶜY and for the mother you would write XᶜXᶜ, and female carrier for the trait would be XᶜX⁺.

Similarly, the genotype of the children would be XᶜY and XᶜXᶜ