@newgeographer2 Thanks so cool! When I enable the 2.5D View, which of the three fills do I need to change? The geometry generator ones, or the simple fill?:)
Example of fill color expression (replace wiki-1.02 with your color ramp):
ramp_color('wiki-1.02', scale_linear(raster_value('topo15', 1, centroid($geometry)),-1500,2000,0,1))