Originally Posted by Jessobear

That has nothing to do with the bulbs, it's the design of the projector itself. All OEM HID's basically use the same 4300K capsule. The purple and blue you see if just a narrow band that is at the cutoff. If you go up close to any of these cars, they basically all look the same. Using a blue of purple high color temp HID capsule makes the entire beam that color. You still won't get that flicker and prism effect you see on other cars. You see that prism effect because as the car bounces up and down, you're seeing different bands of color. The color also never changes to white as you approach the car.

In some cases, changing the lens will make the cutoff much more colorful. For example, a Celica with one of the later factory HID options is not that colorful. A few people took apart the lights and swapped in lenses from an Acura TSX. With no other changes (and an OEM Denso 4300K capsule), the car instantly had intense bands of blue and purple at the cutoff.