I've not ever thought much about this. I'll have to kick it around some. Off the top of my head, I'm thinking it might be Sega Saturn.
Though I don't think I'd vote for any XBox in the OP's poll, I do think its worth noting that I've always really liked the XB green color. When I fire up an Xbox and see that logo and the bright green color, my gaming senses get rolling, and my game mode turns on automatically.