painting only a portion?

Really easy question I’m sure.
2 parts.
1: How do I subdivide only one face of an object? Say I select a cube and only want to subdivide the top portion while leaving the rest of it alone, how can I do that?
2: How do I then color just that part? I’ve tried both multiple times with no success. Any recommendations?

1.select only the faces you want to subdivide, if you’re not using subsurf press y to split the mesh and you will be able to subdivide this without effect the rest of the mesh
If you are using subsurf you cant split it, the edges around it will have to be triangulated to allow it to go from the original amount of vertices to your increased amount.

  1. see the multi materials in blender wiki manual
    link > http://mediawiki.blender.org/index.php/Manual/Multiple_Materials