I always call and get the red removed for the reason that I had a 10 minute time change on the family holiday booking to Greece and some weeks later went into the booking by mistake and saw there was a second, more important change, that the curtain had moved and we had been re-seated from row 6 to row 22. Now re-installed in row 9.
Annoying that you can't clear it online because I presumably ended up clogging the phone lines for other users.
How I miss MyFlights. I have CheckMyTrip on my phone but it doesn't seem to send alerts for seat or time changes.