There's a product used by airlines (can't remember the company) that goes on airplane tires to protect them from UV light and prevent rubber cracking. When applied it looked like permanent tire shine, it is dry to the touch, and is supposed to last years. Maybe someone in the airline industry knows what this is because dry permanent tire shine would be awesome if we can get our hands on it.
i leave the brown. michelins start out black ish, turn brown after a while, and then they turn grey and crack. once they turn grey they also sometimes stop wearing because the rubbers so hard
Do not use solvent based tire dressings on tires, you will get some browning at times.
Try to use water based dressings, even though they do not have great longevity.
Some Michelin tires are hard to get the deep black gloss.
Maybe try {Car Pro Perl}, a thick water based , tire protectant. Use it straight, undiluted a few times.