Messages are highlighted in a light blue to players who are within 12 blocks of the sender (configurable with chat3.near, if set to 0 positional highlighting is ignored). Messages in which the receiving player's name is mentioned are highlighted in a light green, as are PMs. Messages in which the first character is a ! are highlighted in red to all players (also known as a shout). Important messages (mentions or shouts) also cause a bell to be played to players if chat3.bell is true and the player hasn't disabled the chatbell using the /chatbell command. Everything mentioned here can also be configured, and is documented below in the Configuration section.