My lovely boy has this interesting eye phenotype- not quite heterochromia, but one of his eyes is both blue and green (the other is fully green). I was wondering if you knew what might be going on there? If it helps, he's deaf- I've been told that there's a lot of linked genes in deaf cats.
Well, that is heterochromia! It's not full-eye heterochromia though, but still is heterochromia. And you did guess right, it is connected to his deafness (KIT locus is responsible for both!)
Full deafness in fully white cats is often linked to the white dominant gene, which takes away all pigmentation in the cat's fur, and has a chance of taking away pigmentation within the eyes, hence the blue slit.
It has to be noted that these genes aren't connected with albinism. I've seen a person say their white cat with yellow-blue full heterochromia is an albino and it was exhausting to explain it to them. Not albinism. The genes aren't even connected (as it's connected to pointing in cats, rather than white patterning)
Anyways, I'm pretty sure I don't need to tell anyone that the cat is fully white.