Normal headlight bulbs are either made of tungsten or halogen, both of which rely on a superheated filament for illumination. On the other hand, the bluish tint you see on your SRT's headlights is caused by HID (High Intensity Discharge) bulbs, These bulbs have no filament and create light like a mercury vapor lamp- a high-pressure gas is excited between high-voltage electrodes. The bulbs are filled with xenon gas, which is why HID headlights are often referred to as xenon headlights. When you turn them on, the xenon gas turns into white-hot plasma light in seconds. A single HID bulb is so bright that it can handle the job of two incandescent filaments.
They also use less voltage and last for 90,000 miles.