The following presumes you bought the SRX used.Vehicle:
2004 SRX N* V8 - ~97,700 miles
This is my first vehicle w/ HID headlights. I noticed that the driver side low beam bulb does not shine a bright white like the passenger side does. It's more of a purplish color. Is this something HID bulbs do before they are about to go out or would it be some other problem.
It does sound like something is starting to go as HIDs do change colour before they fail. An alternative explanation is that it's a new bulb - HIDs do come in different colour ranges, after all. Are they the same colour when the start up and then one of them slowly changes or are they different right from a cold start? If they're different from start, it could be that one is a replacement. Still, that's not foolproof.
HIDs should last ~7-8 years with average use. If your bulb is at the end of its life, the real question is whether it's your ballast or the bulb that is failing.
The "easiest" way would be to swap bulbs from one side to another (if the bulb burns purple on the driver's side, then it's the bulb; if the purple stays on the passenger side, then it's the ballast). Besides, doing the swap would let you see the bulbs and may help you determine if one of them had been previously replaced. Alas, on an SRX, this is actually far from an easy task... :crying2:
Unfortunately, if it's your bulb that's failing, operating it for too long in a failing state can harm your ballast. Unfortunately, no solution facing you is cheap.
My advice? If you have to swap one bulb, swap them both - it'll keep your lights in the same spectrum and you won't have to do this again for a very, very long time. Ebay is probably your cheapest source for bulbs.