you can't










i'm kidding
there are way too many ways to do it

you can select a face and assign a new material to it

you can use ramp shaders

you can use texture mapping (the most common way to add detail without increasing geometry)

use solid texture synthesis (not a perfected technique yet)

you can assign procedual solid textures (not as fancy as solid txture synthesis and takes a long time before you get something reasonable)

you can't use vertex colouring, which i think is really weird



in short your answer is to assign materials to faces or use texture mapping

i figure you dont know what that means (or you wouldnt be asking) so i direct you to the inbuilt tutorials that come with maya and this one here at this site
https://www.simplymaya.com/movie_page...html?tut_id=94