Thanks. It was being funky at first and only showing Red, green and blue. I was applying the vertex color map first under diffuse and then applying the material to the object. Looks like the material must be applied first and then the vertex map.
You need to apply a Material with a Vertex Color Map to your object. But you can do it after painting. It just tells the renderer to use the Vertex Color. Just use a Standard Material and put a Vertex Color Map in the Diffuse Channel. It should render then.