Vox bleached his hair!

This is a very odd observation indeed, with no rational explanation. Not that the other theories had much grounding either, but I digress...
Anyway, we know that Vox Verlix had blond or light-coloured hair in Midnight Over Sanctaphrax. Nothing wrong with that - but then, in Vox, he has black hair! How does that work, I hear you cry? The answer is simple. Thanks to Cowlquape's hair bleaching, we know that such things were possible around that time. We can also deduce that the amount of bleach that Cowlquape had was small, as he appears to have been conserving it (considering the fact that Cowlquape didn't want to be noticed, which he certainly would have been with brown hair, he should have dyed his roots as soon as they started showing.) Because Cowlquape's hair has gone grey by the time we meet him again, we never find out what happened to his bleach.
I put it to you that Vox Verlix bullied Cowlquape into giving him bleach for his own hair, just because Cowlquape had it and he didn't!
Vox and Cowlquape certainly know of each other; and Cowlquape does seem to have a bit of a bad history with Vox. Vox would find it all too easy to intimidate Cowlquape until he gave him some of his precious bleach; and because Vox's hair was naturally darker than Cowlquape's, it took more bleach to make it the same colour.

There are now several different theories as to what happened when Cowlquape left. Perhaps Vox was only bleaching his hair to annoy Cowlquape. Perhaps he stopped bleaching his hair because Cowlquape, his only source, had gone, or perhaps he found an alternative supplier and continued to bleach his hair. The first two theories take into account the fact that his hair is definitely darker by Vox (the book), but do not seem to support the fact that when we see Younger Vox in the same book, his hair is still blond - so what about the third theory?

I think I have uncovered the shocking truth about Vox, my dear readers. He only stopped bleaching his hair when he had used up all the hydrogen peroxide in existence.