I wouldn’t go the way of duplicating JSON model assets for a colour change as that increases the download size by the size of the JSON.
The best way to do this is to use ‘Entity Materials’ which allow you to change the material mapping of the mesh instances on that entity only.
Project: https://playcanvas.com/editor/scene/646951
Create a new Entity and add the model to it.
Select the Entity and in the Inspector, click on Entity Materials
Click on the mesh instance material mapping that you wan to change
Change the material assignment
And now you have two entities with the same JSON model but with different material mappings
