Just released metacity 2.17.5 and libcm 0.1.1. Grab 'em quick.
The compositor edges ever closer to prime time: As well as other fixes, this version includes a workaround I lifted from Beryl called LIBCM_TFP, in case you don't have texture_from_pixmap, which some people have suggested is the cause of the blue window problem. Thanks to Travis Watkins for the suggestion. I have written a guide to getting delicious compositor goodness on your desktop, which I would like you all very much to read. Let me know how LIBCM_TFP works for you.