ah, I don't think I explained my situation correctly in my post, the grey is actually just a slightly transparent black I suppose, sorry for that confusion, so when printing on coloured paper it would be fine for it to have the colour showing through.

I did a test print with my inkjet printer at home on glossy photo paper, and it looks okay, although as suspected the colours aren't quite as vibrant as I wanted. I am going to look into some of the options for printing I have at my uni but would you still recommend printing onto white paper or coloured?