[Brian]

Interesting - I hadn't noticed that iOS 5 let you control those colors now - nice of them to add that!

I *think* the calendar app tries to use whatever color is specified on the Mac side. All the calendars that I have in both places match when viewed on my iPhone, in any case.

I'm not sure where that info is stored or transmitted, though. I enabled calendar export on my Mac, then took a look at the contents of the file that OmniFocus puts on the server, and nothing jumps out at me as being OmniFocus saying "hey, make this calendar purple".

If you subscribe iCal or some other app (I use BusyCal, personally) to the calendar, then change the color there, it's possible that'll make it's way to the iOS Calendar apps. Sorry I couldn't be of more conclusive help. :-/