There is absolutely no need to incorporate it into Bitcoin Core.
FYI first two implementations were actually in C++ (the first one was a proof-of-concept which modified Bitcoin Core (bitcoind), the second one was Armory-based).
It would take just a couple of days to add a color kernel to Bitcoin Core, but what's the point? How are you going to use it?
There is a need to incorporate it into
btcd, but Monetas is going to handle that.
The point is that Open-Transactions is already an excellent system for managing vouchers and the metadata associated with them, and just needs some kind of objective server-independent representation of them for maximum functionality.
What's going to happen is that OT servers will run btcd nodes in the back end (theoretically they could also run bitcoind, but who'd want to?) and OT clients will handle all the front end functionality.