I'm looking for a way to do an elevation heat map relative to ground surface.

Hey all, first time poster here. I’m working on a project that has the remains of some old stone foundations, using the point cloud I’ve created a sort of elevation heat map with the point cloud, but it is relative to actual elevation, I would like to have those foundations ‘pop’ a little better using the elevation relative to the actual ground. I’ll attach an example, it shows the color by elevation but relative to actual elevation. I need colors to differentiated relative to elevation above ground. Anyone have any ideas?