Hm, tried to have that also happening over here, but I couldn't. There are some issues with hiding and re-showing the chain of windows, though, that I have to work on, but that's not cosmetically, but functionally.
What Windows version and Theme and Shell (Explorer or an alternative?) are you running? as I've only tested with Glass on standard Win7 x64 with Explorer.
I'm using a call of SetWindowPos with (AutoIt3) flags BitOR($SWP_HIDEWINDOW, $SWP_NOACTIVATE, $SWP_NOMOVE, $SWP_NOZORDER, $SWP_NOSIZE) to hide, and $SWP_SHOWWINDOW in the appropriate place to restore the window. That shouldn't touch the background color though.
The standard function WinSetState() was pretty slow, so I searched and found an alternative. I can supply a test-release if you like, using the 'trusted' WinSetState calls?
Oh, and the "Push 1ce" and "shme 2" buttons are shown when you press the red "nger ca" button...
The implicit feature request of shadowing the caption as a tooltip is already scheduled for the next release