Radar

The radar is located in the upper-right corner of the screen. Its position can vary depending on whether you have the UI open and if you have enabled the stretch UI option. The Radar displays your heading, your field of view, and information about objects around you in the form of colored dots:

• White - A Non-Player Killer, a fellow player.
• Yellow - A Non-Player Character.
• Orange - A Creature that can be attacked.
• Purple - A portal.
• Blue - A lifestone.
• Red - A Player Killer.
• Pink - A Player Killer-Lite.
• Green - A member of your fellowship. A triangle pointing up is the fellowship leader. A triangle pointing down is any other member.
• Light Blue - A Turbine-controlled Envoy or any other special character controlled by Turbine employees.

In addition to the dots white, pink and red dots will show up as a hollow square instead if the player is in your allegiance. Hostile players will show up as an X if you are also a player killer and they are not in your allegiance.

An interesting discussion of changes that were made to the radar see here.