Right. I'm getting somewhere (Possibly)
The colours of most things are set in the theme's index.css file, which is in the theme's "css" directory.
Have a look through that. It's well commented-out, so you should figure-out the part you need, fairly easily.
Again, the colours are in Hex format.
Trial-and-error's a good way of figuring that out, as long as you keep a copy of the original file, just in case.
I'm not sure about this "Rank" thing.
What do you mean by "Rank"?