It should get darker naturally over time, IF you wear them often. But since they don't fit well, you probably won't (and shouldn't, for long term health reasons). If you are dead set on keeping them, you might try burnishing the toe and the heel by bulling with a dark colored wax. Any dark color wax will do- black, dark brown, mahogany, burgundy, navy, etc. Best recommendation is to flick it on.