When is the logo light on the tail turned on?

Question

I noticed sometimes aircraft taxi with the logo light illuminating their tail, while others have it off. So is turning on the tail light at the discretion of the pilot?

Answer 1

There can be several lights on the empennage (tail section) of an airplane. There are two as shown here:

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The red light is called aircraft beacon. The white light is called strobe.

When to turn them on is explained here:

All aircraft built after 11 March 1996 must have an anti-collision light system (strobe lights or rotating beacon) turned on for all flight activities in poor visibility. The anti-collision system is recommended in good visibility, where only strobes and beacon are required.

Another one is logo light:

This light illuminates the livery design on the vertical stabilizer.

For more details, please see this question:
When to use Beacon, Anti Collision, Strobe, Logo and Navigation lights?