I recently needed to have 256 color toolbars in my app. If you create 256 color bitmaps in devstudio, and try to use them with CToolbar it won't work.
The problem is in the LoadBitmap() member or CToolbar. Appwizard will create the following line in your CMainFrame class:
It really is that easy, I found this solution after writing my own toolbar class that used the tool control directly, and 256 color bitmaps worked fine. I couldn't believe it, but it works!