I’m not sure there was a proper version of the (Ambiant + Radiant) MATE icon theme compatible with the old way Folder Color worked. I provided the icons that are currently used and at the time they were added, it was during the “switch” to the new icons so I followed the instructions to adapt my own custom icon theme. I don’t remember exactly when they were added.
EDIT: my original post about the issue is there: No proper support for Folder Color
Previously, the MATE icon theme didn’t have color folders icons, so Folder Color used its own ones. I provided proper icons for inclusion in 17.10, so you might want to check 17.04 if it’s still available, or 16.04, though I’m not sure Ubuntu MATE already included Folder Color at the time.