thank you for reaching out to us. The answer is unfortunately, no, you cannot resize a
c4d.VariableTag, i.e., a
c4d.VertexColorTag. You can however create a new instance and copy over data from the old tag, taking the new size into account.
But I am also a bit unsure how your question is meant. When you copy over all point and polygon information from one polygon object to another, then all the old point and polygon information in the object that has been copied to, will be gone. So even if you would carry over the vertex color information, it would not make much sense anymore, as it has been created for the old topology. The crashing you did experience, most likely was caused by overwriting the target polygon object with a vertex list that was smaller than the original one. The
VertexColorTag was still indexing that old and larger vertex set and then came down burning when you switched out the vertex data under his feet ;)
When you want to just join two polygon meshes, including some tag data associated with them, I would recommend using
c4d.utils.SendModelingCommand. If this is not the case, I would have to ask you to clarify what your goals are, because I currently do not fully understand them.