How to edit TextMesh.mesh so I can change vertex colors?

I want to edit the vertex colors of a TextMesh's mesh so I can create gradients and change text color by letter for cool animations/ fancy graphics.

However, I can't seem to find a way to access the output mesh of the TextMesh component, and I have spent close to an hour searching for it so I am pretty stumped right now.

Is there any way to get/ set a Text Mesh's mesh? If so, how? Also, I would prefer not to rely on third party extensions.