Is there a way to change the color scheme in different regions of the same plot?

So I've made a matlab plot that looks like this: http://i.imgur.com/8S4WzrA.jpg.

This is a plot that shows symmetric complex data with the magnitude information on the upper triangle, phase information on the lower triangle, and a (mostly) constant coefficient along the diagonal. My question is, can I change the color scheme for each section? For example: shades of red for the upper triangle, shades of blue for the lower, and grayscale for the diagonal? Also, would it be possible to have an individual colorbar for each of the sections? Thanks!