The ornamental design for the alternating light trailer hitch cover, as shown and described.
FIG. 1 is a perspective view of the alternating light trailer hitch cover of my invention fitting into a broken line showing of a vehicle and hitch mount. The broken line showing of a vehicle and hitch mount is included for the purpose of illustrating environment and forms no part of the claimed design;
FIG. 2 is a perspective view of the alternating light trailer hitch cover of my invention, with no lights illuminated;
FIG. 3 is a perspective view of the alternating light trailer hitch cover of my invention, with only the left light illuminated as shown by the darkened circle;
FIG. 4 is a perspective view of the alternating light trailer hitch cover of my invention, with only the right light illuminated as shown by the darkened circle; and,
FIG. 5 is a perspective view of the alternating light trailer hitch cover of my invention, as a reverse view based on FIG. 2.