I’ve done some prototyping like this in the past.
Mash has the lost tama which wears from red to black.
As Nova said terra has a battlescar pill which wears from white to red.
It’s quite challenging as adding many paint coats makes the tama overly heavy. It also takes a very long time to wear through each layer.
I will take a second stab at this and start with an abnormally small tama and throw loads of chippy paint on.