Hi Paul, 

Thanks for asking. One volume file can contain several different non-overlapping ROIs, so that we can set colors of each specific ROIs. To do so, the volume file should be carefully prepared, that each ROI should be labeled with different numbers. (e.g. voxels in ROI1 = 1; voxels in ROI2 = 2...). Then in the volume panel, enter the number of the labels that is wanted. The color can be changed for each ROI by selecting them in the pop-up menu. 
Please let me know if anything unclear.

By the way, I can't open the attached file. It said: "The Attachment does not exist".

Best,
Mingrui