help with colorbar and polygons

I'm somewhat of a newbie and I have hopefully a simple question (people asking
similar questions in the archive seem to be beyond this already). I have a
working color fill generated using the set_facecolor command on a collection of
polygons. When I try to use colorbar() I get the message: cmap = mappable.cmp
AttributeError: 'NoneType' object has no
object 'cmap'.

This question could be a little lacking in information? Maybe someone has a bit
of sample code that already does something like this?