I’m not sure what’s going on with this surface, but there’s something up with the colour. It was created in a script using the OffsetSurface method. Not sure if that matters.
Notice how I can’t change the colour of the surface until I extrude it.
Here is the file:
Colour anomaly.3dm (192.2 KB)
I should mention that this is Rhino 7 SR6 (latest RC)