Target Indicators and HUD Icons
Target indicators used to be thin line brackets, and robots got them whether you could see them or not.
The brackets are now bevelled corners with a dark outline: red for robots, purple for the reactor, green or the team color for players. A health bar above the target runs from green through yellow to red. The target a homing missile is tracking is marked with a dashed yellow ring that slowly turns.
A robot only gets indicators when it is actually visible on your screen, and the same test decides which targets homing missiles can lock on to.
The weapon and inventory icons on the HUD have got frames that show their state: the selected item has an amber frame, items you don't have are grey, and empty ones are red.
Target indicators are set in the cockpit options: none, for missile targets only, or full.