I have either five or six MBs. (Every color, including grey, but yellow) I can use them interchangeably.
Bands are linked to the account. Admission is linked to the account. Nothing is on the bands.
We had four checkins in January and I was ill most of the trip and not thinking well, so at checkin I would just pull out any band (too sick to remember what the "right" one was), they would do something to check, it would be fine and we would move along.
Sometimes things glitch, but that's just a glitch.
Any band linked to your account should be able to be used whenever.