This is interesting, yesterday I could change the colour scheme when the towers were all quality 1 and it was a 3 star resort, but a bug made me have to start over. Now it's a 2 star resort with fully upgraded towers and I can't do it. I tried switching services off and reverting them back to quality 1 but it's made no difference, and also tried it with a fresh new world too but I don't see that option anymore. I am absolutely certain that the option to change came up when using CTRL+Shift+left mouse button, but can't remember if it was live, build or buy mode. This is a complete mystery to why the option vanishes like this. I read that star rating may affect if the option appears or not and isn't always the case. Sounds like a bug in the game to me.