Speaking of Half-Life², I've just refreshed the color scheme here on the site to a palette inspired by the game. In fact, it's more than just inspired—the background image is derived directly from a screenshot (manipulated, of course).
I've always been a fan of the steel and orange look of the HL series, so I figured I'd give it a shot here for a while. I might continue on this theme and pull some more color variations out of the game in the near future.
And note: This color variation still contains the "invert colors" feature, which might make it easier to read for those of you who prefer dark text on light backgrounds. You can find the invert colors option in the footer of every page. It will set a cookie as well, so you don't have to keep clicking it. Of course, clicking it again will set your colors back to normal.