Rest assured, I don't think anyone's hard-coding any new colors. There are just some old ones lingering.
I got rid of most of these a few years back, but I know I didn't get all of them; it's a big codebase.
If you find something like this, and it's causing you trouble, /msg me the details and I'll see about
getting rid of it. If, after a week or so, it's not fixed, and you haven't heard bad news from me,
/msg me again. I don't mind a bit of polite hassling. :-) You might also talk to the pmdev folks, who
might respond more quickly. If a patch is brought to my attention to do this sort of thing, I'll apply it.