Here is a thread when I asked. I then decided not to do it and just used these seat covers. It gave me the look I wanted but left the original seats original with no damage or aging that I am led to believe might happen with dyed leather as it gets older.
Check with your local dealership and see if they have a service who touches up interiors for them. We found a fellow in Central Illinois who restores leather and fabric seats and panels. He does fantastic work. We have used him for auto as well as aircraft interior repairs and touch up work. He can take a faded, but not worn out, interior and make it look like new. He even repaired a burn hole in a fabric seat without having to replace the out of production panel/fabric.