That would be great, and I’d be happy to do whatever is necessary to help this become a reality, e.g. contributor agreements etc.
I’ve just updated the gist to reflect the latest cleanly-applying version of the patch.
The current defaults on OS X make little sense IMO, and result in inaccurate colours for pretty much everyone AFAICT.
My understanding is that everyone who cares about colour accuracy on OS X builds his Emacs with an sRGB patch of some sort. As for making this a build option, I don’t even think the non-sRGB colours should be an option on OS X, though I can’t speak for the whole NS platform.
-Steve