window reflection plugin... if you enable this plugin, you will notice that any windows that you group/tab will no longer have a glow, but instead you will always see a black halo around all of the grouped windows. color changing with a keystroke combo does not help. all groups will all be black. disable window reflection plugin to fix this.
this bug only seems to affect xorg, xgl appears to be fine.
As this is a Compiz Fusion plugin problem, could you please report it at the Compiz Fusion bug tracker at http://bugs.opencompositing.org? Thanks.
Sidenote: This seems to be a driver problem to me ... it works fine here, and the fact that it works fine with Xgl also seems to back that.
window reflection plugin disables grouping glow color