If you want them to look like the real thing, instead of something someone dyed at home, smoke them just like they were originally. I prefer using cedar that has rotted on the ground and is kind of chunky, and a little pinky.
The advice about hot water is not correct. I was given a bunch of commercial tanned buckskin years ago, that was as yellow as a school bus, and slick as a salamander. I decided that since I didn't have anything invested, I could do a little experimenting. I had made a pair of buckskin leggings ( slick side in) out of some of the leather, but they were way too yellow. So, I thew the leggings into a washing machine full of hot water, with some Rit dye remover. When they had been in for the prescribed time, I removed them, and hung them on a cloths line in the shade. They looked kind of green, but all the bright yellow was gone. The green color faded when they dried, and after I wore them a while I started getting compliments on my brain tanned leggings.
I am an advisor for the Order of the Arrow in my area. So, we do a lot of native crafts using buckskin. We have found that chalk line chalk, and masonry tint, powder rubbed into the nap of the leather does a great job of adding, or changing color. Surprisingly, it doesn't easily come off when worked into the nap of the leather with a cheap throw away chip brush with the bristles cut back very short. Just, work the powder into the nap in small circular motions, and don't get it where you don't want it, its not easy to get off.
Hungry Horse