LoL I'm in a nutty coloring mood.
And the color of his clothes here are a sign of that. But I think....well Wizarding clothes are really abnormal...if you're a muggle. So...I dont think wacky colors are out of the question. I mean...I don't think Voldemort or any of the purebloods went about saying "Okay. We HAVE to wear black. We're gonna wear black and look sinister and when we do wicked things we'll all go BWAHAHAHAHAHAHAHAHAAAA!!! with our heads thrown back and our arms in the air."
So..judging from Dumbledore, the wizards that Vernon sees in the first book, Lockhart and Snape I've decided that....Regulus Black is not afraid to wear the colors. And depending on the character, colors will go according to that. Example: Lockhart is extravegant and insane, pink blues and yellows. Snape is angry and gothic and full of dark rage, Black black black and more black...McGonagall is sombre, wise but sometimes very excitable(as in when she's watching quidditch or yelling at Moody/Crouch Jr., greens, tartans and I think dark reds and browns. Lucius is snobbish, rich and wicked. Dark greens darker purple and reds.

okay...sorry about that..
I think his clothes are cool but I think he's a weenie. And being related to one of my least favorite characters doesn't help.