I was really sad looking at my gray finder sidebar. I thought that this release of Finder was designed by some engineer from Soviet Union or North Korea but, finally, I found a solution to get back my colored finder and also my smile!
Take a look to this link: http://osxdaily.com/2011/08/25/get-color-sidebar-icons-back-in-mac-os-x-10-7-lion-finder-windows/