Vertex colors do not render in the scanline or mental ray renderer by default in 3dsmax.  Nor is there a switch to enable them.  So, I built a script that tweaked the selected object or scene’s materials to allow this.

Interface Shot:

Material Change:

Results:

The screenshot above has a Advanced Lighting Radiosity pass baked down into vertex colors that were tweaked using the Vertex Color Tools Suite script to augment hue, control blending, and fix problem areas.

The render maintained the vertex colors, allowed over-brightening, and added cast shadows.