b2.75 # b9bccd5 Gooseberry.
MBP OSX 10.10.5 Intel Iris pro
When changing User Prefs > Theme > UV Image editor > Scope Region Background Color, there is no effect on the scopes in that window.
The default color does not provide enough contrast with the graticule, making the display difficult to read. So it is important to be able to change the scopes background.
Confirmed on other system but no details of that system available.