Apologize for the double post. I just found that I can load the colormap I want using the "Load..." button in the ROI drawing pane. So, that prevents the need for the "hack" to the main code I described above. 

Now, I suppose I can create a custom colormap within matlab in which each ROI value/color is determined based on scaled colorbar, then load that text file using the "Load..." button.  Let me know if you have any other thoughts on this!  Thanks again!

-Ben Conrad