Yes you can bruise a tooth and I've done it numerous times with a front tooth that's crowned & root filled. It can be very sore for a few days but then it's like it never happened. I don't know what colour it would be if live, but I'm sure there's nothing that can't wait until you see the dentist on tuesday. I'm sure that the worst that can happen is they may need to crown it.
It's really great that you are getting a mouth guard, it should give you great relief. Make sure you wear it every single night - you don't want to lose your teeth when it's so easy to prevent!