I've tried to export the theme from Windows 7 and import it to Windows 8, but some colors are still different. In particular, the Active Window title bar color is too similar to the Inactive color.
I've also tried to edit the colors section of the theme file directly before importing it (see here). However, Windows 8 seems to ignore the
Control Panel \
Colors section unless HighContrast is set to on. Turning HighContrast on breaks everything, though (text becomes unreadable).