yeah i know the stuff you're on about, a metallic flecked strange paint. the most common colouring is a purple to green shift i think. I guess it would work well as a case colour, as long as you got the edges etc all trimmed in nicely. you might have a problem with the paint not sticking to any plastic surfaces on the PC, unless you sand or prime them first in a more thorough way than the rest of the PC... however if your mate is a sprayer he will be well aware of these considerations.... go for it i'd say, it'll be unique...