Hi Rob,
A subject I covered at length! Colour, taken from Vosper actual plans, is BS631 Grey, although over time, I bet it changed slightly. Cabin roof were originally intended to be yellow, then went to grey, and ended up white. Finish was "cerrux" which was none slip on decks, so its a matt finish. Rear well deck was planked, as was the area where tow hook is located. For cosmetic appearance I cheated a bit and went gloss finish on the cabin roofs, might have been a bit slippy for the crew!
Here is the colour, I achieved the none slip finish using the paint in the picture, just kept doing dust coats till I arrived at the texture I wanted, then painted over in BS631 which I had made as an aerosol by a local paint mixer company. Cabin sides where indeed a darker grey, but once I did this it looked like I had made a mistake, just didn't look right, so did it all in BS631
I have a load of plans, pictures etc, and my build blog is on here somewhere, so just ask,
Paul