Broadway play?
It’s a difficult question to answer (and brings to mind an old BlackAdder exchange about the blueness of the sky vs. the blueness of the Blue Stone of Galveston…) But here goes: Genuine arc-discharge (also called metal-halide HID) headlamps run with a very purplish-white character that reminds of the color of the electronic flash on your camera, because the same technology is at work (an electrical arc jumping through an atmosphere of Xenon gas). But despite the purplish appearance, this light is actually white with a discrete blue component. That is to say, the vast majority of the output light from an HID headlamp is a good, solid *white* that is closer to the white of the sun than most halogen bulbs’ output spectra can reach. And, in addition, there is a separate output spectrum of blue-green to blue-violet frequencies that is a byproduct of metal-halide lamps such as the HID lamps currently used in cars. That blue-green to blue-violet frequency band is “throwaway” light in an HID
