Those new colorless iTunes icons sure do rub some people the wrong way. Not to worry, there is a ‘fix’ out there. You simply download a new iTunes.rsrc file and shut down iTunes and replace it with the one you’ve just downloaded. When you restart, its like you’ve never updated (except Ping is still there).
We haven’t tried this (we are in the ‘who cares’ camp) so use at your own risk. via OPM
PS. Bonus tip from the comments: If you want the normal stoplight buttons back, Close your iTunes, open Terminal and paste in this “defaults write com.apple.iTunes full-window -1”, hit enter. Boom. Open you iTunes. Fixed.