I was going to suggest Color by Robert Craig, but it is semi-permanent and won't lift color either. It can, however, turn those grays into nice, natural-looking highlights if you use a very light shade.

SF Bay Area, CA * "The Angel-Goddess-Guru of Haircoloring"
3b/c/a mix. medium texture, low porosity
My Motto: Strand Test! some hair pics
-- gone, but never forgotten.