“But his Senna’s custom emerald paint —a $300,000 upcharge, for its technically complex tint that exposes the carbon-fiber weave below—wasn’t found in nature. Fux was visiting McLaren in Woking, U.K., and a particular green paint (originally developed for the P1) wasn’t coming together for him. Fux promptly pulled off his own, green shoe and plunked it down as a makeshift color swatch.”