[Brian]

I'm not an engineer, but to the best of my knowledge, the only time the calendar subscription info is touched is when the "Subscribe in iCal" button gets tapped. Apple takes a very dim view of apps messing with other apps' data in an automated fashion or without permission - if OmniFocus were doing that, I think it would be very likely that they'd reject the build.

That said, it can't be a coincidence that the colors are matching on my various devices. The color getting stuck on whatever Calendar picked first is certainly possible; I'm just not sure how to get it un-stuck.

Yeah, the more I look into this, the more I think this may be a Calendar-on-iOS issue. I changed the color of one of my 'regular' calendars on the iPhone and it changed color on my iPad. When I tried the same procedure with a non-OmniFocus subscribed calendar, the color ended up out of sync on the two devices, and I lost access to the "Custom" color I had set.

I had to re-set the custom colors using BusyCal on my Mac, then push that out to iCloud and wait for the iOS apps to notice the change.