How to get separated mesh vertices to interact?

So I've imported t$$anonymous$$s object into Unity that is about 400,000 vertices. Unity has automatically broken the mesh into 13 pieces to remain under its 65,000 vertex limit. I'm trying to visualize vertex coloring in time along the entire object, and have a script written for vertex coloring in time.

I wanted to know if anyone has any ideas for how to make the different vertex arrays of the different parts of the mesh interact. As it is, I attach my vertex coloring script to each different part of the mesh and color each part individually. What if I want to color the entire object as one object? Can I combine all of their vertex arrays into one? Can I combine the meshes somehow, despite Unity's 65,000 vertex limit?