Top Area around the Address Bar Grey Color! Rated 1 out of 5 stars

Top area around the Address Bar: Grey Color!
Bottom area: Light Blue Color.
Why the colors are Not the same?
Like the ones of Vista aero skin?
(https://addons.mozilla.org/en-US/firefox/addon/4988)

See the ScreenShot:
http://img525.imageshack.us/i/48636067.jpg/