I mean they are nice when they are new and clean, but they need quite a bit of maintenance to stay that way and mostly end up grey, especially if you don't use soap powder with bleach in it like Fairy non-bio or something. I use an eco-ball, and it makes colours look fab, which is why I do like my coloured nappies. I can't imagine only having white.
I have to admit, i only every use white/natural nappies :) Infact i spacifically ask for white.
firstly, it means no colour runs (since i only ever wash nappies with nappies) I try to dry my nappies on the line in the sun (when we have it) so they always look lovely and white (even the worst stains always disappear (even though i only wash at 40)- whereas a colour nappy would fade with that treatment then i figure i'm going to cover it up with a wrap, so it won't be seen, so what's the point of lots of colours, then having to worry about whether it looks ok with the wrap (eg colours showing through a white wrap)
Now colourful wraps is another matter - these can be stuck in the wash with everything else, dry very quickly so i just hang them for a few minutes indoors and you can see them - all you have to worry about is not putting colourful wraps on under white baby clothes (which i also love - once they start crawling they'll probably never white again until they're 18, so best wear white now)