Another bootophile here. If I had to, I'd say you need a minimum of two pairs:
- Dress boots. I have a classic pair of knee-high black Sudini boots with 2" heel.
- Casual flat boots. Something like the Frye Veronica.
If one only had two pairs, they'd most likely be in neutral colors, to go with most of your wardrobe.
That being said, I have way more than two pairs of boots Colorwise, I have:
- patent dark gray
- slate (khaki)
- blue
- dark cream
- black
- brown
And coming soon:
- white
- red
So no, I don't stick to a particular color palette. Although most of them are on the cool side in their respective color families.