From Warren Harding:

Re: Reflection is key to jewel beetle colors, scientists say (July 24): This sounds like the car paint we call “Chameleon” here in New Zealand. It’s been around for at least 8 years. It’s very expensive (something like $1,000/litre) but you do see it from time to time especially on show cars. As I understand it, you first paint your car black, then apply this paint which is clear in colour. Something to do with the thickness of the clear coat and the distance the light travels through it including the reflected path length makes the reflected colour different depending on the angle of incidence (which affects the path length). I think that’s how it works. So I don’t think this is a new idea unless this works a different way.