For what it's worth, I don't take dreams and hallucinations to involve seeing at all, so I don't believe I have anything to explain with regard to colour in dreams and hallucinations. I take the question "Do you dream in colour?" to be incoherent whereas the question "Have you dreamt of colour / coloured things?" is fine. The former question presupposes that perception involves seeing internal imagery rather than directly perceiving the world, which I deny, and that dreaming / hallucinating can therefore be said to be a form of perception also, something which obviously can't follow from my denial of mediating imagery.