As I pointed out in my DUH moment, you can get different colored tubes and switch them around for variety as long as they are the same diameter. The tubes are inexpensive, it's the caps that are pricy.
Yeah, i love the variety of tube colours. I think i'll probably get one standard tank, one XL and then an extra tube for each in different colour patterns. One of them is definitely gonna have to be that black that you have - i hate to copy, but it just looks too good and the chances of me ever running into anyone with the same design over here are practically zero
Actually, there would be an excellent opportunity for a UK vendor to sell them over here on behalf of IBTanked.