As those of you who have Lion may have noticed, Apple has removed the color from many of the system icons, including the Finder sidebar. Luckily this is reversible.
The name of the plugin for SIMBL that allows to return the color to the Finder is ColorfulSidebar, and the truth is that for lovers of pre-Lion aesthetics it is a very interesting addition.
It is really easy to install and once installed, you don't have to do anything to make it work.
Download | SIMBL and ColorfulSidebar
Source | OS X Daily