Comment 35 for bug 236046

I modified the latest svn version to fix this problem for other themes than Ambiance. Transparency doesn't work, but now you can change the background to whatever color you want. The file is in attachment.

Save the file to your home folder, then open a terminal, copy it to /usr/bin (sudo cp checkgmail /usr/bin) and make it executable (sudo chmod +x /usr/bin/checkgmail) . Now you can restart checkgmail, set the tray background, and restart again.