I wouldn't pay much attention to how the exported models look, it's quite likely that they've just done something incorrectly during the export that's broken the textures/shader. I think you're right in that it's using vertex colours for blending, although even if it's not, that's going to give you the effect you want…
Hello I exported a model from zbrush as obj when I import it to marmoset, the texture does not load and it's only White. what is the problem?! Did I export the mesh in a wrong way?