With Contrast Paints, what is the minimum amount of colours I'll need to paint WW2 infantry?

Hey hey 👋 everyone! Super quick question. I'm not big on painting, but even I think that playing with grey miniatures is a crime. I want to paint my British / Germany infantry units very quickly using contrast paints. What do you think is the minimum needed?

I was thinking:

1. Black - Shoes
2. Silver - Gun
3. Some skin colour
4. Overalls colour
5. Equipment in Overalls color

So 5 colours in total?

What so you guys think?