Wookie got combed a lot last week and the dandruff is gone. As I mentioned before, the reddish tint to his fur is from nutrition problems and his previous starved state. The eumelanin, which is a pigment that makes his fur black was probably not produced sufficiently. He should darken as his condition improves.
Brushing him made me aware of some other anomalies in his fur colour. As I said to 
The grey is also noticeable behind his ears although the fur looks like it's becoming darker at the roots.
There are a couple of possibilities here: firstly, the silver could be what is called fever coat: this is when the mother was ill before the kittens were born and had a high body temperature, or he had a high temperature after birth. Given that all his siblings died, this is a possibility. Fever coat is not a sign that his health is compromised and he will outgrow it in a couple of months.
I was wondering whether his mother's Siamese genes were at work but it seems that Siamese pointing genes are recessive, which means that he needs a copy from each parent for the pointed coat patterning to express itself. Another genetic possibility I considered is the dilute gene, which produces gray cats, but also sometimes cats with dark faces and silvery bodies. I read that this is also a recessive trait so it's unlikely, because his mother carries siamese pointing genes
Another possibility is that he has a smoke coat and will be permanently silvery around the edges. It could be that that his father carried a "smoke" gene. This is when a black cat has a silvery undercoat. Smoke genes are dominant, so he only needs one copy of this gene for it to express itself.
Time will tell whether he becomes all black or smoky. I think he will be a smoky cat because his claws are not all black. Pure black cats without any white patches generally have black claws too. It will be interesting to see how Wookie turns out.
Wookie says: I'm just going to keep playing while you overthink this
He's doing well otherwise and I'm grateful because we have just been put under fairly hard 14-day lockdown thanks to seriously surging covid cases. The jokers in my town have taken to calling my city "Wuhanesburg" but jokes aside, my vet had to close for a few days because she and some of her staff got covid. My niece and many friends and acquaintances have it too. Although he should be vaccinated, I'll wait 2 or 3 weeks while the mess subsides.