We seem to still use a gradient for the frame images on supervised user themes. For normal and incognito themes, we switched to flat colors, so supervised users should probably get the same. I'll see if I can post a screenshot later. In the meantime, here's the asset we're using for the active frame.
 

Deleted: theme_frame_supervised.png 219 bytes

	theme_frame_supervised.png 219 bytes View Download