The ornamental design for a multi-color boat anchor, as shown and described.
FIG. 1 is a perspective view of a multi-color boat anchor according to the present invention, wherein the shaded portion is a first color and the unshaded portion is a second color, the first and second colors being different.
FIG. 2 is a right side elevation view thereof;
FIG. 3 is a left side elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a front elevation view thereof; and,
FIG. 7 is a rear elevation view thereof.
The broken lines illustrated show portions of the multi-color boat anchor that form no part of the claimed design.