Alchromancy’s colors are deposit-only and semi-permanent: they add, and lift nothing. No semi-permanent color lightens, and for the full result on dark hair the hair must be lightened first, which is its own work, and not part of the Rite. What each color does on each base is set out on its own page.
Our colors are not made to conceal gray; on gray hair the color is translucent and partial. The Collector Edition's pages, "Of the Vessel," speak to this.
Hair that is porous, previously lightened, or damaged takes color faster and deeper, and lets it go sooner. The result depends on the starting color, the hair’s porosity, and whether it has been colored, lightened, or chemically treated before.