As Jim said, white is appropriate. If you can remove the printing on the PVC pipe, that would be nice. If not, painting it white (to cover the printing) would do as well.
Note that at 15" wide, the stick would look fine at anything from 1/2" through 2 inches, though my favorite would be 1 inch. Reason is simple - 1 inch is sturdy enough to handle wind blowing against the 15 inch sail and would keep its straight look, but not look too odd against the size of the prop.