Low lights

Hi:  I don't know of an over the counter kit (sold in a box at stores like Target).  You'll probably have to go to a Sally's and buy a bottle of the color you'd like and the appropriate developer and then apply your lowlights.  Also, if your hair has been artificially taken to the platinum level, you'll need to add back some red/gold tones (a colored protein filler) for any darker colors to take well without leaving the hair a grayish or greenish color. 

If you'd like to review someone's journey from platinum to a slightly darker light ash blonde through the application of lowlights then do a search on posts from Kelly H.  You can use the search tool to quickly pull up the information.  I would highly recommend reviewing her posts so that you might learn from her mistakes and successes.  Good luck!  Maria