It was transporting marijuana?

So the operator can see it in the sky?

Beacon for the operator? Light for the camera (particularly if the operator was like "crap, is that a helicopter right in front of it")? Reflection of the helicopter's starboard (green) position light? Reflection of a white light (searchlight?) off something on the drone (marijuana, green structural elements)?

Here’s a turbine fpv setup hitting 500kmh

https://youtu.be/TFYXiJ1NJTw