I wanted to change the stock HID's to a whiter color; I don't like the dull yellowed look of the stock HID's. The stock bulbs produce a light at 4300k temperature color so I replaced the stock bulbs with 5000k temp bulbs which are crystal white right on the edge of blue.
I like the color change but there was a drop in lumens so they don't put out as much light as the stock ones do. It's not terrible but I noticed it. The stock bulbs are 35 watt so I'm looking into upgrading the setup to 55w but that will require changing the ballast too.
In the meantime here are a few pics to show the difference. Obviously they're much brighter than in the pics; I changed my camera settings so you could see the colors easier instead of just bright glare.
The first pic is the stock HID 4300k bulb:
The next is the 5000k bulb:
Here you can see both before I changed the driver's side; the 5000k bulb is on the left and the 4300k is on the right:
Makes for a nicer, "more alert" kind of look I think.