Hello,
Not too many meal worms they can be quite hard to digest unless you get them nice and white. Wax worms, full of fat so be careful.
I would try locusts. We have a cham that just suddenly refused to eat crix.
Veileds like most chameleons have a specific set of colours they can adapt as necessary. So Veileds will always be dull greens, browns with slight yellow until they need to change i.e stress, attracting a mate etc.
Some of the ones showing those bright colours on the posts above show the...
Is he only dark when he sees movement ? Is there anyway you can peek into the room without him seeing you ?
He is still young and everything else seems fine.
Its a great feeling when they to finally trust you. Hand feeding is a great way to start also just sit next to the viv with the door open. We have had several chameleons that when they spot us will actively "run" towards the glass and bang on it to come out.
Never fed our on WC insects, you can buy them online same as crix etc. Far easier to handle than crickets too.
I would be worried about flies too, you never know what they have landed on.