Why do the headlights of BMWs, Audis, and Mercedes always look so colorful?
The lens curvature at the edge bends the white light producing a “prism effect”. White light is broken down to its fundamental colors. Blue light is high energy, and thus is absorbed last, traveling the furthest. With this prism effect, you’ll notice that the projectors you see on BMW for example are only purple and blue from the sides, the top, and the bottom, but are always daylight white on the road and in the beam pattern. This phenomenon can be demonstrated when you watch an oncoming BMW hit a pothole or speed bump in the road and the car’s nose pitches up and down. The headlights will flicker and “throw colors off”, but returns to a solid-white beam pattern directly on the road. Trying to obtain all the color from just a bulb is not only incorrect, but also dangerous because the more color there is to the HID bulb itself, the less light output there will be.
