Not a design I would go with personally.. but I like the idea.

Mine would say "bloody hot"

 

found the stuff here

https://www.proto-pic.co.uk/thermochromatic-pigment-black-20g.html?gclid=CM30gMvCtc8CFecp0wodft4D-w

it turns transparant when heated, so you paint whatever underneath, put on the thermochomatic top coat to cover.

 

I have enough hassle just keeping exhausts black.

Would only work on a trailer queen.

Ah, cool - I was wondering how they did such detailed work with paint that would be invisible unless hot!

Don't that sound like a  static engine,,