A further graphical indicator for the various PvP situations are the differently coloured frames around characters.
- Yellow frame
- your own character and summons if you are in an active PvP situation
- all characters and summons that you have attacked or that have attacked you
characters and summons who have attacked another character of your guild or party
all characters and summons that participate in a PvP situation in which you are not involved; e.g. members of 2 other guilds fight with each other
Source: Tibia Manual