/chatcolor [player] [modifiers] - Change yours or a player's chat color!
Note: Please see here for information on hex colours! The format is like so: #RRGGBB, where each character after the # must be a number or letter between 0-9 and a-f.
/chatcolor - Shows your current chat color!
/chatcolor gui - Open a GUI for selecting your desired color!
/chatcolor - Adds or removes a modifier from your chat color.
/chatcolor available - Shows your available colours and modifiers!
/chatcolor commandshelp - Shows command help! You can also use /chatcolor help.