Window Blinds custom color question

Even though I have several dozen WB skins installed, I find that I use only a couple of them, for one reason: Window backgrounds. I am referring to the area in, say, Outlook in which your Inbox and email text is displayed, or the actual page you type onto in Word.

Some skins that are otherwise great make this flourescent chartreuse or dark grey. It looks great, but it makes it really hard to get any work done. Other skins leave it bright, glaring white. That is just too bright. A few skins (Attacker is the best, the new Copperdeck is good), on the other hand, color it a subtle shade of grey, dark enough to cut the glare, but light enough to work against.

My question, then: How do I go about taking a skin that I really like that has an unworkable color for these areas and force it to use a subtle grey? Doing so would allow me to use ten times the number of skins I use now. I have been digging through all the menus on WindowBlinds, but am unable to find the setting to adjust this.

FYI, running WinXP Pro. Thanks all, for the help.