I think it's a bit hard to go past the original white toilet. I certainly wouldn't go for anything bright or something that would date easily. Bunnings have the following toilets which offer a nice bit of colour to the item...
Mondella has a black toilet coming. It looks striking. Not sure whether it would be easier to keep looking clean or harder?
Isobel, I'm loving this orange? toilet!
My wife and I were in Italy last year and we saw some of these in a place we are staying in Capri. They matched the decor of the shower and the whole bathroom and even the fittings. It all looked pretty cool. Typical Italian style.
I reckon if it's tastefully done there shouldn't be any dramas with the way or the colours that you choose for your bathroom. After all, who cares what other people think anyway?
Besides, black is not a colour, it's a mixture of all colours.