@MWilson:
An avisynth script like colourlike, or there are other softwares that could do that. Today I reviewed the EP 6 deleted scenes included in the Rinzler ebooks, and luckily the b&w ones could be not used, as they are uninteresting or alternate takes, BUT the Rancor scene has shots not seen before, that will be great to reinsert! Your chromajig works well, but I think it’s impossible to reach good result with automatic colorize tools… I think that doing manual settings is the only way to go, possibly following a reference image/clip.
You are absolutely right. I would have to work in Photoshop. Just a starting point☺