Colorizing the extruded material

Hello everyone,
How can I colorize differently an extruded part of my 3D object?

Example: I have a SVG file of a map region. In order to create a 3D view of this region I used the classic extrusion process. However when use the colorization tool, all the object takes the same color. I would like to have a different color (white for the map and gray for the side(depth)).

The other problem is that blender thinks that it is still a line (not an object), therefore, when I try to mesh it, it doesn’t take it as 3D object but as a line (SVG source file).

Any ideas?

Thank you in advance

Convert to a mesh (Alt+C) then add two materials, assign one to the sides and another to the face

Yes! That did it. I was confused with the material section. Thanks a lot.

Thank you very much. It did it! I think I just messed up with the material section.