I don't think it's so much the colors as the designs. Bright colors help, absolutely, and there certainly have been less of them in recent years, which is a shame, but if you changed the red and blue stripes to black and white ones and the red gloves and boots to brown, he would still be recognizably the Destroyer - just muted a bit. Batman's costume has never been terribly colorful, even during all those years his cape was colored blue instead of black, but he has one of the most distinctive designs in comics, so it hardly matters. The Hulk has been green, grey and now red, and he's worn all sorts of outfits besides the classic purple pants, but through it all, he's still been easily recognized as the Hulk. The problem is not so much the colors, it's the fact that popular designs tend to get blatantly copied over and over again, so eventually (as in certain points in the '80's) everyone is running around with Wolverine's hair, Batman's gloves, Cable's arms and the Punisher's guns, and it's hard to recognize anybody. Either that, or they go the opposite route, and opt for plain, unornamented jumpsuits, which makes things even worse. A distinctive design can really help a character, simply because it elevates them above the crowd.