Outside linebacker Josh Martin was signed off of the Colts' practice squad today by the Jets, so Indy replaced him by signing offensive tackle John Wetzel to their practice squad.
Tuesday is the Colts' off day, and while sometimes there's significant news coming out on that day (such as Pep Hamilton being fired or Andrew Luck having a lacerated kidney, both of which were announced on Tuesdays), it is typically a time for teams to evaluate players and tweak their rosters.
The Colts didn't make any major changes today, but they did add a player to the practice squad, signing offensive tackle John Wetzel.