What does the envelope of a speeding ticket look like?

I know I’ve been caught speeding (only 33 in a 30) last week and am waiting for the ticket. What colour is the envelope and is there any indication on the envelope that it’s from the police or contains a speeding fine? Thanks Reddit!!

Edit: Thanks for all the replies. A few things to clarify if this helps. I think I was going about 33 but it’s outside a school and is known to pick up anything over 30.I also think I saw a flash I live in the south West of England if that makes a difference!