Aircraft Lighting Systems and Cockpit Lighting
External lighting
Navigation lights are red on the left (port), green on the right (starboard) and white at the tail. They must be on from sunset to sunrise, and whenever the aircraft is moving on an apron. The anti-collision beacon (red) and white strobes warn others; switch strobes off in cloud, fog or on the ground when they dazzle. Landing and taxi lights are for illumination, not for being seen, and add a significant electrical load - check the alternator before selecting them.
Cockpit lighting
Flood lighting, post lights and instrument backlighting should be adjusted so instruments are readable without destroying dark adaptation. Red light preserves rod vision best, but red light makes red and brown chart features hard to read, so use a dim white map light briefly if needed. Carry a serviceable torch with spare batteries, and know where the standby lighting or emergency torch is.
Worked example
After engine start at a dark apron you select beacon, nav and taxi lights. The ammeter shows a slight discharge at idle. Reasoning: the alternator is not yet online at low RPM and the combined load is high. Reduce non-essential lighting, raise RPM to bring the alternator online, and check the ammeter before selecting the landing light for takeoff.
Traps
Leaving strobes on in cloud and causing flicker vertigo; turning the floodlight to maximum and losing dark adaptation; assuming the landing light will not affect the electrical system; relying on one torch; and not checking panel lighting before departure.