Do you know where this is located in the Win8 theme?
The aero like overlay on the control panel
Edit Vista / 7 Control Panel and Navigation Parts
(branding is the glyph or image you can add over the side bar image)
You can also change the text colours of that area too.
Change skin colours/Edit colours/ when the edit colours window opens, down the bottom you will see a button that says "Edit vista/7 part colours"
click on that button.
a new window pops up. and the first section is called "control panel"
that is where you change the colours for that area.
close and apply when you are done to see results.