Unfortunately, this is the behaviour of the SIMBL plugin.

> One oddity about this solution is that you may need to kill the Finder
> again to bring the color icons back after a full system reboot

[Source][1]


  [1]: http://osxdaily.com/2011/08/25/get-color-sidebar-icons-back-in-mac-os-x-10-7-lion-finder-windows/