I don't think so
I've messed around with this for a solid two weeks for a side project of mine, and I've decided that the Finder sidebar selection colors are drawn programmatically by Finder itself and that therefore users will be unable to change them to anything other than the two defaults OS X allows.
The reason the menu bar selection colors can be changed (among other things) is because the actual selection is an image stored deep within the System file structure along with the aqua buttons, checkboxes, etc. images in
Code:
/System/Library/PrivateFrameworks/CoreUI.framework/Resources/ArtFile.bin
Code:
/System/Library/PrivateFrameworks/CoreUI.framework/Resources/SArtFile.bin
Code:
/System/Library/PrivateFrameworks/CoreUI.framework/Resources/ArtFile200.bin
(ArtFile200.bin for 10.7+ only). While these image files are encoded in this strange bin file, this guy
alexzielenski has created
a bash script to decode and recode the ArtFile.bin, ArtFile200.bin, and
SArtFile.bin files. So it's entirely possible and incredibly easy now for programs, scripts, or users to decode these files, swap in the images with the new hue and color they want these resources to have, then recode them. The changes are reflected upon logging out and back in. Finder sidebar selection images are not in here though.
Not all Aqua resources are stored here however. There are numerous blue resources scattered everywhere such as
Code:
/System/Library/PrivateFrameworks/FinderKit.framework/Versions/A/Resources/
for what seems to be deprecated and unused Finder sidebar selection images and some other blue resources, but regrettably changing these resources and plenty others scattered literally everywhere throughout the System directory had no effect on the Finder sidebar. I eventually got desperate enough to look through every image in the System directory by hand to exhaust every possibility to no avail.
Because of this, unless the Finder sidebar selection images are also encrypted in a different strange file in some obscure location in the system, I'm certain that this image doesn't exist and that the selection is drawn by Finder programmatically. Sorry to be the bearer of bad news, hopefully with the impending UI refresh in 10.10 we will see a more reflective system where the global "tint" of the system can be changed easily to reflect the wallpaper or preference of the user (much like iOS 7), but until then we're stuck with the hard coded blue or graphite. If anyone out there has a correction or something to add please do so as this is just my own findings and might not be the whole picture.