The ornamental design for a taillight for a vehicle, as shown and described.
FIG. 1 is right perspective view of a first embodiment of a taillight for a vehicle according to our novel design;
FIG. 2 is a side perspective view thereof;
FIG. 3 is a front view thereof; and
FIG. 4 is a side view thereof.
FIG. 5 is left perspective view of a second embodiment of the taillight for a vehicle according to our novel design;
FIG. 6 is a side perspective view thereof;
FIG. 7 is a front view thereof; and,
FIG. 8 is a side view thereof.
The broken lines are for illustrative purposes only and form no part of the claimed design. Also enclosed is a set of photographs of an embodiment of the invention.