My model with SPIN: 2QHNM98J6 is a WRL file using material colors per primitive. The central tetrahedron should be yellow (and printed as such some years ago) yet the new(ish) previews show the entire model as uniform red. I downloaded and re-checked the model file already, this is an error on your end.
I went ahead and escalated this issue to our 3D tools team. Hopefully we can track down what happened here and prevent it from happening again.