Notice in the preferences how there are different tabs: "Daytime" "Sunset" "Bedtime". Just click those individual tabs and drag the slider to be whatever you want for the color!
Very strange. I am using the same vintage of machine (and have been for a while) but I've never seen what you're describing on mine. Do you have any special settings, or is there anything in particular you're doing on this machine (like a lot of videos, or an unusual web browser, that sort of thing) ?