There's currently proximity, global, clan, and group chat. Friend chat will, as well as others will possibly be added in an update in the future. In order to switch between chats, the player must enter the F1 key for Proximity, F2 for Global, F3 for Clan, and F4 for Group. If player has a clan and online members ingame will be able to read the message.
Also, added in the 5/7/13 patch is voice proximity chat in which it is possible to hear and talk to other players that are within a 200m radius of you. When communicating through voice proximity one must be cautious because a voice icon will display above the player's head when speaking, giving away their position. This form of communication can be enabled or disabled in the settings menu and the default "push to talk" key is T. Players can also be muted by hitting tab, selecting the player's name, and hitting the mute option.
You can use html like "<Font color="#ff0000">" to speak in red or just "$" for blue. (As of 12/12/12 this does not seem to work, confirmation needed)