Here's the U.S. Naval Academy's guide to the rules of the road.[1] Section C has the lights. For most ships and boats, it's reasonably simple - red, green, and white visible in 120 degree arcs, with white visible from the rear, plus a high white masthead light for some vessels. The complicated cases mostly involve work boats doing something - fishing, cable-laying, towing, etc.- where there is a hazardous area around the vessel and movements are restricted.

[1] https://www.usna.edu/Sailing/_files/documents/2019_OSTS_Docu...