When encountering other vessels in darkness what do visible white and red lights indicate?

Answer 1

In not knowing the configuration of the lights you are looking at, it is hard to answer. If the red light is lower on the vessel around the bridge, you maybe seeing the vessels port side (left) running light. The white light is going to be either a masthead light or possibly a stern light. However if the red light is much higher, atop the mast, then this could indicate more than a few different scenarios.

Lights & Shapes

Rule 21-International

Definitions

(b) "Sidelights" means a green light on the starboard side (right) and a red light on the port side (left) each showing an unbroken light from right ahead (000 degrees) to 22.5 degrees abaft of the beam on its respective side. In a vessel of less than 20 meters the sidelights maybe combined in one lantern carried fore and aft of the centerline.