Warby: Connect the colorSet[#].colorName from your objects shape node to cpvSet[#] in a mentalrayVertexColor node (you find it in the "textures" tab of the mr nodes) Then hook up the outColor from that node to whatever you wan't it to control.
Here you go. I hope this helps. (Don't forget to assign the material to the object) EDIT: You might not have a cpvSets[0], but if you connect it directly to cpvSets it will create one. Or just hit the "Add new item" button in the mentalrayVertexColors node first.