I suspect the answer is "you can't" but I thoguht I would try:
I have a 3D scanner, and for some client work, all they need is the 3D geometry (GrabCAD: yes!), but for other work, our clients need the 3D model with the associated color/texture (GrabCAD: ???)
Is there a way to show an .OBJ with .MTL and associated texture file on GrabCAD? I really don't want to split my models between Sketchfab (highly optimized only for non-CAD models) and GrabCAD (which is far better both for CAD models as well as sharing files privately).
I don't know about textures but when I upload the step files that Inventor creates GrabCad is able to display colors similar to what I used in my model in their 3d interface. Maybe something like YouTube would work if the client doesn't need to be able to manipulate the object so much as just see what it looks like.
I am referring to UV texture maps as found on 3D scans, etc. The coloration of CAD models via materials works great on GrabCad but I am not seeing if the texture maps are supported. I really don't want to use two different services (sketchfab for textures and Grabcad for CAD models) but that may be what is needed.