Airplanes lend themselves to complex livery. The lines of the body and wings make for an interesting surface to be decorated, and some aircraft owners go for pretty wild paint schemes, which can be awesome.
But sometimes simplicity works better. Polished aluminum with a few simple lines of paint can make an airplane really stand out. Too little paint can looks sketchy, and too much can be garish; one must strike the balance.
Thie P-51 hit it out of the park. A few lines of black paint and the Air Corps insignia accent the lines on the body and nicely compliment the mirror-shined aluminum for a striking effect.
I love these planes anyway, but this one was pretty hot even by Mustang standards.