I bought a small amount of leather paint/dye from the company below because my shift lever was very tatty. I didn't go for an exact colour match but it worked fine and still remains so many years later plus I still have 70% left in the bottle.
If you look at their website they do offer quite a few off the shelf colours for Lexus models but also offer a custom matching service if you can supply a small sample perhaps from under a seat.
I think they also do various leather repair kits.
I also bought a bottle of leather aroma spray which comes with a pump action spray bottle, makes the car smell factory fresh again, I think everyone who attended the last midlands meet tried it out.
I recently obtained a quote from a local leather specialist to have all my seats repaired/refurbished,the front passenger one now has a split in one of the base panels and they quoted £550.00 to replace the panel and sort out the others, I suppose I could get away with leaving the rears as they rarely get used but then may have matching issues.
Anyway the link
http://www.dynamixdyes.com/leather-colours-12-w.asp