Try to find SEM brand. You can usually find it at better automotive paint and supply stores.
Ask the clerk about what to use to reduce//cut it and at what ratio he would recommend. Remember to thoroughly prep the surface you are applying the dye to. -- :thumbs
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.