Plot contours on surface of volume

Thanks, this looks like it will be fairly close to what I want! With regards to the steps you listed when I click on the colour editor toolbar nothing happens. Any idea what might be wrong with my data or the way I have things set up?

Eventually I would like to have the contours as lines rather than have the whole volume filled with colour (so that I can represent a different data type simultaneously beneath the contour lines), is that possible?