Hi,
importing vertex colors is not really supported in VRED at the moment. However, you can give the FBX format a try. It will convert the vertex colors to our internal ambient occlusion and indirect illumination colors. However, the vertex colors need to be in a very specific format to be of any use. The rgb channels of the vertex color should contain the indirect illumination arriving at the object while the alpha channel needs to contain the shadowing data. I am not sure if you can actually force Maya to put out the vertex colors in this format.
Kind regards
Michael
Michael Nikelsky
Sr. Principal Engineer