Shampoo reducing grey hair

There are a lot of new Shampoos in Asian countries claiming they reduce grey hair and restore its color back. The ingredient's list is not written in most of them. Some of my friends have used it and it looks they really make hair black again. 

My question is what ingredient in these Shampoo make hair color black and how they do it?
Is it safe for hair?

Here is an example of such a Shampoo.

Just For Men Grey Reducing Hair Colour Shampoo

Ingredients: Water, Disodium Lauryl Sulfosuccinate, Decyl Glucoside, Cetearyl Alcohol, Glycol Stearate, Ethanolamine, Cocamidopropyl Hydroxysultaine, Guar Hydroxypropyltrimonium Chloride, Sodium Cocoyl Isethionate, N,N-Bis (2-Hydroxyethyl)-P-Phenylenediamine Sulfate, Acetic Acid, Aloe Barbadensis Leaf Juice, Chamomilla Recutita (Matricaria) Flower Extract, 1,2,4-Trihydroxybenzene, Cetearyl Glucoside, Erythorbic Acid, Sodium Sulfite, Phenoxyethanol, Caprylyl Glycol, Stearamide Amp, Panthenol, Manganese Sulfate, P-Aminophenol, Sorbic Acid, Etidronic Acid, Fragrance.
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