Recently the subject of tinting skins created for Flex has cropped up a couple of times.
Here’s a little class I threw together that enables this from Flash. Instead of extending UIMovieClip you can extend UITintedMovieClip. This new class will look for a style set on your Application class named skin-tint.
In Flash you then create all your skins in greyscale and the class then uses ColorTransform to tint itself.
UITintedMovieClipExample (right click for source).
This class only handles tinting of one color, but its feasible if the skin creator used MovieClips inside the skins with a defined naming convention, different tints could be applied to different instances.
I’ve also added the class to our Google Code repository.