Get vertices a material is assigned to

Hello! As the title states I am after a solution on how i can get all the vertices that a material is assigned to. This because I want to be able to change the vertex colors just for that part. The reason being is that I'm creating a mobile game with cars, where I only want 1 draw call for the body, but i still want the ability to change color of the car at runtime, except windows, lights, grill etc (so I can't use a shader with a main color, and i don't want 2 materials for the body). So if I somehow can save a list with these vertices would be great. Thanks in advance