In the post CommandBarButton.Mask property deprecated in VS 2010 I mentioned that VS 2010 will deprecate the Mask property of CommandBarButton to specify bitmap transparency, accepting 32-bit bitmaps with transparency in the alpha channel in the CommandBarButton.Picture property instead.
The VS team told me some weeks ago that the CommandBarButton.Picture would accept also in next VS 2010 builds 24-bit bitmaps with RGB=0,254,0 (almost pure green) as transparent color (as VS has always accepted for commands). I have verified this week that VS 2010 Beta 2 accepts that possibility correctly.
Bottom line: VS 2010 will accept both in Commands (AddNamedCommand) and CommandBarButton.Picture:
- 32-bit bitmaps with transparency in the alpha channel
- 24-bit bitmaps with RGB=0,254,0 (almost pure green) as transparent color