How much do materials impact performance?

I don’t understand. Why would you only need one material? How would it then be possible to blend different colors together?

This asset here

has gold around the engines, blue as the main color, black streaks, grey highlights and silver up front by the nose. How could you get that with only one material? (I’m not going to use that asset just an example)

This model here is the exact look I’m going for with simple but clearly different color

I see atleast 5 materials, but maybe I’m missing something.