Yes, Rusty nails left in vinegar for a while makes one color tint and clean iron nails makes another. The vinegar and nails work by bringing the natural tannins out of you wood to show more. Lots of people use fine steel wool also. Other things that can make a stain when boiled in all kinds of combinations. are the inner bark of Blackjack Oak, Sumac berries ect. Lots of stuff. Most of this kind of stain raises a wood grain fuzz that you just hit lightly with some steel wool but work beautifly. I have a board out in the garage i was playing around with painting test stripes with this kind of thing and I could get anywhere from Yellow, bluish all the browns, reddish black and grey. It was amazing what can be done with one trip to the woods. Made the house smell woodsy too when I boiled this stuff can try it with vinegar then water might make another color. You can web search natural plant dyes the ladies use to make hand dyed yarns for ideas what to look for if the nails don't do it for you. I built a kicker box for my daughters picup and matched her grey carpet perfect once playing around.
Put it this way, Minwax will never get another dime from me. lol
We used steel wool and vinegar to "Antique" some wooden doors in our house. I let the concoction sit for several days before using and it came out great!