Just For Men Control GX Grey Reducing 2 in 1 Shampoo and Conditioner $6.47 AC (or $5.59 for 25% more at Target YMMV) + Free Shipping with Prime or FSSS

https://smile.amazon.com/gp/product/B0829LV2SZ/
Clip the $1.50 coupon to get this deal. Looks like most places are selling the 2-in-1 version for $7.99.
The normal size is 4oz. Target has a 5oz version on clearance for $5.59 but it seems very YMMV. It is only available in store and only 1 out of 20 stores in my region has it in stock – https://www.target.com/p/just-for…A-50437275
Innovative hair color shampoo that gradually reduces grey with every wash
CGX reduces grey gradually, for subtle, natural-looking results, unlike other dyes
It makes reducing grey radically easy: all you have to do is shampoo your hair
Triple Patented Formula with Hemp Oil and Arginine. This product is best for Light Brown to Black hair.
Just use it instead of your regular shampoo until you like what you see. Then alternate with your regular shampoo to maintain the look you like.