As said, light grey is best. Although I have excellent results with a plain white one. I'll get some pictures up of a film. Another thing to consider, which I found out, is the colour of the room you are in. My cinema is a conservatory and I wanted to watch movies in the day time but the blinds just wern't dark enough, so we blacked them out with thick white card on the windows and all on the roof to blank out the roof lights, so now the room is one massive, dark, but also white room. It's fine being dark, but when you fire up the projector, the light bounces off the screen and then off the white walls of the room and then back to the screen again, so you get a brighter more washed out image. So, paint your walls matt black and have a good screen and you'll be on winner there.