I purchased the Hair Mayraki Anti Grey Restoring Treatment and tried it.
The product definitely has a coloring ingredient in it. Everything that the product touches (Towels, Shirts, T-Shirts etc) get stained. I used it on my beard that it definitely make it much darker but it is as if I dyed it. I don't know if it restores the natural color in time because I could not use it for a long time due to the stains (that even do not disappear after washing) on all my shirts, towels etc.