Is there a way to change the icon color in the Finder navigation bar?
This MacOSXHints article may help. To summarize


Install SIMBL (version 0.9.9)
Download ColorfulSidebar
Copy ColorfulSidebar.bundle from the Disk Image to /Library/Application Support/SIMBL/Plugins (or ~/Library/Application Support/SIMBL/Plugins
Restart Finder


It also seems that the change may get wiped out after a reboot, there's an example for a LaunchAgent script to prevent this on the MacOSXHints site.