After struggling for years with premature gray hair, worrying about looking old at a young age, trying different supplements, the gray hairs just keep coming. I tried the Just For Men gel, regular dye, and I felt very artificial. It's pretty obvious when men dye their hair to cover grays, and IMO makes them look like pansies. In my experience, I have learned to embrace it. It gives a distinguished look, and it is an unspoken sign of experience and wisdom.
Welcome to my world, human life. Starting with your youthful locks of dark hair, everything consisting of molecules will slowly but surely start to fall away from you. Like the song says, you dont know what you got till it's gone. I bet before you noticed a gray hair, you never really gave much thought to your original hair color. To me, graying early has better prepared me for everything else I will lose before I leave this world. Literally EVERYTHING.
Try black sesame seeds, b12, tiger balm, etc., but ultimately, sooner or later you have to accept your humanity and your genetics. Also focus more and have more appreciation for the things you still do have, rather than what you don't have. Don't wait till it's gone to appreciate it. There is no such thing as time. Albert Einstein said the distinction between the past, present, and future is only a stubbornly persistent illusion. Accept it and embrace it.