I simply can't abide Lion's/Apple's dedication to monochrome sidebars everywhere in Lion. The SIMBL technique still works in the Finder, but the new 10.6 version of iTunes breaks all the previous hacks I've tried. What I'd love is to be able to edit the iTunes.rsrc file (and similar) myself but I don't know of any way to do that in OS X. Is there a way to edit (copies of) .rsrc files? Failing that, is there a way to change the depressing gray sidebar icons in iTunes 10.6?
You could try ThemePark
Down with Aqua! ThemePark lets you give your computer a style of its own.
Use ThemePark to create or modify the way Mac OS X looks, as well as to change the appearance of individual applications. Just draw titlebars, buttons, and other widgets in the graphics editor of your choice, and move them into ThemePark to create a new theme or modify an existing one. Also use ThemePark to safely apply themes to your operating system.
Not sure it will do the job, I read about it here.