Hi solid-honey,
To my knowledge, the Color Vertex Tag is not very useful here if painted.
If you can convert it:
https://help.maxon.net/c4d/2024/en-us/Default.htm#html/55293.html
Then it is easy; have a look here; I have set up the example from a Color Vertex Map. If only Black and white, why not use directly a Vertex Map?
Perhaps you share a little bit more.
In any other combinations, the results (if at all) are not stable.
All the best