I'm very excited by the functional design principles and keyboard shortcuts that are being implemented for Unity. And function of use is more important to me than looks. However, after experiencing the aesthetic beauty of the display of the top panel in gnome-shell, I was wondering if users would be able to alter the color of Unity's top panel?

IMHO it does not look as good as the gnome-shell implementation (or mac OS X/iPad). I think if an alternate color/appearance were chosen for the panel, it would make a big difference aesthetically.

Is there a way to make it Black like gnome-shell? Or are the color choices limited to theme-designs as pointed out in this answer?

For efficiency and clarity, the Panel should be better differentiated from application controls. The panel should be a different color because it has a "constant (always present) state," unlike application controls. For contrast and easy-recognition, I would like to make the Panel black (like gnome-shell) but make the application controls (e.g., those of Firefox) "Inverted"