"Flames glided in the river, small green flames, red flames, white flames"
Navigation Lights, 1943
Public DomainNavigation Lights (1943) - Credit: HMSO

These are the reflections of the navigation lights of vessels.

Sailing vessels were required to carry a green light on the starboard side and a red light on the port side; steamboats carried an additional white light on or in front of the foremast.