Hello,
OP. Not sure what exactly you are looking for, so here is a big list for you. These masques are all off lexicanum under the Notable Masques section and most of them have a decent picture for color schemes
http://wh40k.lexicanum.com/wiki/Harlequin.
Dreaming Shadow - mauve and green/blue-grey with yellow and white accents. No diamonds at all.
Frozen Stars - this is the masque I am going to do with a few changes made to it - black and white with gold accents, no diamonds (I generally dislike gold, so I intend to do each harlequin with a different colored bright accent and with nebulae and starscapes on important models and vehicles instead)
Reaper's Mirth - white and purple with pink/red accents and no diamonds
Weeping Dawn - blue, pink, and green with no diamonds but have black stripes on the blue - looks suitably crazy as is to not need the diamonds in my opinion (also a good point as to stripes working)
Winter Sun - no pics, but they are supposed to be almost invisible in snow so I would guess whites, greys, and silvers
Laughing Circus - no pics and potentially all dead since no one really knows what happened to them, but I would go with a scheme based on modern circus ringmasters: predominantly red with black and gold/yellow accents
One of my favorite bits about harlequins is that their color schemes do not have to be that cohesive or nice to look at. They're often gaudy and tacky and ridiculous in colors that are seldom seen on tabletop. Make them as whacky as you want.