I think black, camel/beige/nude, something textured, and something bright. If you have all of that, you are probably set for most occasions.
I was the queen of black bags, but I have been branching out. At the moment I have a couple of black bags, some grey (charcoal, light, and gunmetal, python), dark purple, electric blue, beige, muted orange, and blue crocodile.
Mine used to be black and brown, until one day I discovered the delight of bright colors. Now I have a bright pink and a bright orange. I really want a nude or beige one too. Sometimes I find the bag I like look better in a specific color. I'm not sure if Im getting the point across