pcolor() does not return an RGB image. It displays one. If you display a matrix though, pcolor chops off one row and one column so you're better off using image(). I never use pcolor for displaying images for that reason. I don't really know what you're doing because you didn't attach a screenshot. If you have certain kinds of data that pcolor is meant for, it might be fine, but I find it very deceptive for displaying 2D arrays of numbers.
If you do want what pcolor displays as an RGB image, I think you can use getframe().