I'm customizing my Xubuntu theme. With GNOME Color Chooser I can change most of the default option regarding the colours of windows background. But seems that for some special widows like Volume Control, Ubuntu Software Center I don't have any possibility to control the background and the foreground colour. Unfortunately, I don't know why, they have a very bad colour combination (white foreground in a light grey background see figure) so I don't see anything.
How can I change the background color of these "special windows"? Even a default scheme for these one for me goes well but not white over light gray!