The Arena could be a different colour (not Font) due to it being a place to avoid (Maybe this is showing
Michael's Map, so he'd have printed it in a different colour as a warning) or that it is occupied by enemies to the Tower, in the same line as the Maller's Mall and the Colony (seeing as they are both the same colour as the Arena).
Tommy's house may be placed there due to it being heavily mentioned and to show how far
Kelly and Tommy had to go to reach the Tower, just for context.
Don't let me kill the theories though, I'm just playing Devil's Advocate.