would be a cool feature to enable a “paint/stain” on top of your material preview, so the underlying color would be the material color and the paint/stain would remain on the uncarved parts, the visual and contrast in the preview would help a lot
if my material color is “pine”. then the light tan color would be in carved parts, and the paint/stain is white which would show in the preview as white where it is uncarved
I have used the two color acrylic or the 2 color HDPE for this purpose under your material selection,
Thanks for the tip!