* Make sure the Color menu is accessible on GrayScale device, in the event
one would have inherited a color-enabled settings from another
device...
* Warn on startup if color rendering is enabled on a grayscale device.
A non-exhaustive lists of things such a setup would break:
* same-to-same blitbuffers for pretty much every rendering engine
* same-to-same blitting codepaths and fast-paths
* software dithering in CRe