Hey sorry, just noticed the reply. I have a decent start on creating interiors for this but haven't worked on it in a while. Hopefully after I finish my current side project I will have more time for procgen, I miss it!
And yes, Voronoi is awesome, but sometimes tough to get it to do what you want. Regarding colour harmonies, I was pleased with how quickly I could pull that system together, the cities wouldn't be anywhere near as nice to look at without it.
Thanks for the comment