Boil in a pint of water a handful of rosemary; when cold, strain and bottle, but do not cork it. Renew it every few weeks. Wet the hair with it every night." It is doubtful that this recipe would change the color of your hair, but it couldn't hurt to try. Rosemary is still recommended in modern herbal hair treatments (though the expected result varies), and it shows up in many culinary dishes. So, unless you have an allergy, here's an old-fashioned recipe you could try.
Source: Hale, Sarah. The New Household Receipt-Book. London, 1854, p. 209