Thanks for bringing this to my attention - I just tried ColorFaker on my iMac running 10.10.5 and was unable to get it to install the helper tool. I vaguely recall having this issue a few years ago, and logging out and logging back in solved it. Really, there isn't much I can do here - that's an assertion happening inside of CoreGraphics.
Given that ColorFaker will no longer work in 10.11 due to System Integrity Protection, I think the best thing to do is to put a giant warning in the README and discontinue development. It was a decent hack back in the 10.8 and 10.9 days, but I don't want to go around crashing people's apps.