The ornamental design for a paint can holder, as shown and described.
FIG. 1 is a front plan view of a paint can holder of the present design the horizontal encircling structure shown in FIGS. 5 through 7 has been omitted for ease of illustration;
FIG. 2 is a right side end view of the paint can holder shown in FIG. 1, the horizontal encircling structure shown in FIGS. 5 through 7 has been omitted for ease of illustration;
FIG. 3 is a back plan view of the paint can holder shown in FIG. 1, the horizontal encircling structure shown in FIGS. 5 through 7 has been omitted for ease of illustration;
FIG. 4 is a left side end view of the paint can holder shown in FIG. 1, the horizontal encircling structure shown in FIGS. 5 through 7 has been omitted for ease of illustration;
FIG. 5 is a front top perspective view of the paint can holder
FIG. 6 is a back top perspective view of the paint can holder; and,
FIG. 7 is a back top perspective view of the paint can holder shown in FIGS. 5 and 6 in use, wherein the broken lines are the environment of the paint can holder shown in use and form no part of the claimed design.