I know that Orange will now supply custom coloured rims with their bikes, but has anyone had any rims powdercoated themselves?

I'm thinking about getting a pair of 717's done – they're eyeletted I know, but I don't care if everything ends up coloured so long as it doesn't cause a problem when I build them up… Might the existing (black) anodizing cause any issue?

I suspect it would have to be stripped first then coated

The aging (heat-treatment) for 6000 series alloy is done at approx 180 to 200 degrees celcius. The curing of some powder (plastic) coating is done at approx 180 to 200 degrees celcius.
Therefore the alloy will be overaged (heat-treated just beyond its best)once it is powder coated.