The Labels section in the preferences is your friend and you can manually hack the prefs file in an text editor, too.
If you close After Effects with the color changed, it will remain changed the next time you open After Effects on that machine.
The Option to change the color of the import from Creative Cloud Library is the only one that is not available in the preferences.
Sorry for this issue. Did you ever find a solution? Please let us know if you have or if you still need help.
No I did not find a solution because as Mylenium pointed out, that Option is not available in the Preferences.