I’m going to pretend to be an expert here and give you advice. Feel free to ignore. This is all assuming you are modeling olden days, relatively outback, not fancy.
For color selection, Rooster turned me on to the Sherwin-Williams Vintage collection [link]. I used one of those for the color for Mackenzie’s Mercantile (my Mik build from last year):
But when you have more than one building, it would be useful, imho, to contrast the colors: light vs dark, warm (orange, red, yellow) vs cold (blue, green, purple). I did some of that in my previous Mik build:
It also seems important to have a variety of different roof types. In both of these I used a mix of corrugated, tar paper, wood shingles, metal. From reading Model Railroader Magazine for decades, it was constantly pointed out that the main thing people see are the tops of things and that making the roof interesting goes a long way toward making the model interesting.
Another rooster suggestion: don’t do any fancy contrasting trim colors (as you would see in a Victorian house) so the trim (door frame, window frame) should be the same as the wall cover. It is good to have some of the doors be a different color (aka plain or stained wood) as that helps with variety.
Anyway, my $.02 if it is useful. Not that I’ve done that many buildings.
Perhaps others can chime in with their approach.