Why do sidebar folders turn white? Sometimes, not always, when I drag a file to a sidebar folder, it turns white.  The folder I'm dragging into turns white, and it doesn't turn back.
  I have to delete the folder from the sidebar, and then re-import it, and then it's a normal color.
I have no idea why this happens, but you can go to Finder > Preferences and select the Sidebar tab. At the very bottom of the window will be a "Recent Tags" option with a checkbox next to it. Uncheck the box and it's fixed.