Are these models paint-able?

I'm a big time Warhammer 40k player and a lover of tabletop games and miniatures. As such, I was wondering what type of plastic was used to make these models. It appears that the main heroes are already painted but the little minions look like they're kind of just a basic grey color.

Do Rioters think it would be possible to base and paint these minions like you would a normal tabletop figurine? I think it would be a lot of fun to have some interestingly colored minions running around on the table.