Okay, I have a real problem with how Shuichi's gang-rape was handled in the long-run. It was obviously introduced to add to the drama and maybe in a way for Yuki to connect to Shuichi as the same thing had happened to Yuki. But I thought it was completely unrealistic for Shuichi to go about his life like normal and have no long-term trauma over it. Meanwhile, Yuki had basically a personality transplant after his own horrible experience. Then the mangaka herself seems to forget that Shuichi was raped in later volumes as it's repeatedly emphasized to Shuichi by numerous characters and including himself that he would never understand Yuki. Consider they were both victims of gang-rape I don't know any other person other than Shuichi who might understand what Yuki is feeling! So what was the point of even introducing such a plotline if it was only unrealistically short-term and it's never brought up again, whereas Yuki's own trauma—which took place longer before Shuichi's—remains front and center of the major story-lines?
What color is Shuichi's hair, really? In the anime, it's just pink the whole way, and that's fine. And on the manga covers, it's also a mostly pinkish/red color. But his hair, in the manga, is definitely shaded in black. Now, I went with the option that maybe it was just pink hair shaded black, because I've seen that in other manga before. But then, he runs away to NY, dyes his hair blonde, and when he comes back to Japan, dyes it back to black, claiming that black was his hair color when questioned by a character who had met him in NY why he was dying his hair black. This isn't going to haunt me my whole life or anything, but it does bug the heck out of me. What's going on with Shuichi's hair, dammit!?
I read somewhere that Shuichi's natural hair color is black. He dyes it red to fit into his rockstar persona, but with the hair dye his hair is more magenta-colored than red. He dyed his hair blonde because that was his response to Yuki breaking up with him (much like how in some manga series a girl will get a haircut if she's rejected by a boy she liked). When he went back to Japan he washed out the blonde hair-dye because Yuki asked him to return to Japan, and since he'd dyed his hair blonde out of sorrow from losing Yuki it wasn't necessary to be blonde again. So to properly answer your question, Shuichi's natural hair color is black but he dyes it a lot.