I've done this when younger. Two adjacent nails (ring and middle, or middle and index) in one colour, the other three a second colour. I've alternated colours too, but wasn't so keen on the outcome. I've also done all different colours and textures, which can be fun with a very plain monochromatic outfit.
Recently, I've seen French manicures of clear/nude varnish with rainbow-coloured tips. Fun! I also saw a version in all-colour, where this lady had used glossy blue-black and matte green --- one hand was green with blue-black tips while the other was blue-black with green tips. Interesting!