So are you wanting to replace the Apple default sidebar icons with the sidebar icons from pre OS X 10.8.
This may work. Firstly disable the colourfulsidebaricons9 in the /SIMBL/Plugins folder first, i.e trash it.
And Restart to make sure the default grey icons are now showing.
You would need to replace the ones in Core Types Bundle> Resources with those of the earlier OS.
For them to take you then need to locate the com.dock.iconcache and also the folder com.apple.iconservices and delete them.
Restart your mac, these two files will be regenerated and the new coloured sidebar icons should show. The location of the file and folder mentioned above are by default hidden, so you will need to reveal hidden items, if not already done so. Or you could use the Go To Folder function in Finder and enter /private/var/folders, press Go. This will show the location with a further three folders. I do not have Yosemite installed so cannot give you the exact name of the folders to look in, but, for me, I am on El Capitan at the moment, if you look in the top folder, there is another folder with a random name of letters and numbers, in that folder there are another three folders named O. C and T, look in C and you should see the two items mentioned earlier.
SIP will need to be disabled.


Apple do not take part in these communities, and as Yosemite is an old OS (it no longer receives updates) Apple are highly unlikely to implement coloured icons to an operating system they do not actively support. If they were to relent then it would only be to the next or future OS's.