The buttons are normally the blue you have in the image above, I have dragged the
channel 9.msdn/forums page to the Win 7 taskbar as a shortcut. Upon launching this, the buttons are yellow. I also know that they are green also at times, but I am yet to determine the conditions that trigger
a, b or c or is that b, g or y (blue, green or yellow gold)
The tabs themselves also change colour pretty dramatically sometimes, and again, i'm not sure why?
Button color, for an instance launched from a pinned site or desktop shortcut, takes the predominant color from the site's icon (so, if you pin C9 to the taskbar, you get yellow buttons). It uses an algorithm similar to the one that decides the color of
the taskbar button highlight.
Tab color is arbitrary; all tabs in the same group will be the same color. This behavior's inherited from IE8.