I've had excellent results with Leatherique on my 1995 seats. There was supposed to be some kind of coating on the leather, but the leatherique soaked in nicely and softened up the hardened leather in a couple of segments that I suspect was sun damaged either directly or from the interior getting too hot. I could almost not believe the improvement.
It is a bit of a process in that you have to keep applying it until it stops soaking up the conditioner, and then apply the cleaner to clean off the excess, but the results have been worth it to me. It took about 1/2 dozen applications the first time, then just one when I did it every 6 months after that. It also works much faster on a hot day, although I got it to work in my garage by putting a small heater in the footwell.
Leatherique claims to not affect the color, but I'd definitely try an unobtrusive spot first. It definitely affected my color, from sort of old looking to like new! There is no obvious coloring in the products.
It worked so well, I used it on my living room couches too.