The ornamental design for a colostomy accessory, as shown and described.
FIG. 1 is a top plan view of a colostomy accessory of the present invention according to a first embodiment;
FIG. 2 is a bottom view thereof;
FIG. 3 is a side elevation thereof, the other side view being a mirror image thereof;
FIG. 4 is a rear elevation view thereof; and,
FIG. 5 is a perspective view thereof.
The broken lines shown directly adjacent to the claimed portions in FIGS. 1 and 5 illustrate the bounds of the claim and form no part of the claimed design. The remaining broken lines illustrate portions of the colostomy accessory that form no part of the claimed design.