I think it's a setting you have to apply at some point, like "apply this to the tag "background" for the background to be in the good colour. I had this problem once at school and that what I had to do, I kept trying to have the good colour, I was always selecting the good colour and everything but when I was clicking on okay nothing had changed, and the teacher said it was because I had choose I don't remember what setting instead of "apply to a tag". After I picked that setting, I would chose the tag I wanted the setting to apply to (header, background, title...) and it was okay!