Render color per vertex in mental ray® for Maya®using the mentalrayVertexColors node. It can be used in a shading network for rendering color per vertex. As a result, you can store shading and lighting information on mesh vertices (rather than shading networks), simplifying your scene and making it more efficient to render.
To use the mentalrayVertexColors node
If you want to force the export of all the CPV data for all the meshes in your scene, you can turn on the Export Vertex Colors attribute in the Render Settings: mental ray tabs, Options tab, Translation section. Exporting CPV data can be process-intensive, so do not turn on this attribute unless necessary.