Just read a message asking what product or process is ahead to darken a bit the seat's brighter red section. After seeing the color patch from Corbin before ordering and also seeing it was their only red leather option I checked with a local leather guru. He makes tack for show horses. Amazing and sometimes gawdy stuff for a hobby that puts to shame any concept that we really spend much for or on our bikes.
Anyway... This old guy has been doing leather longer then I've been doing. When I asked him if a new leather could be darkened and done so where it would be permanent, not bleed and not cause other maintenance or long term care issues he looked at me like I was some kind of idiot.
Not knowing whether I'd asked something that was obviously possible or obviously impossible I proved the ignorance by asking again. He tells me the product to use is something called Hydrophane Leather Darkening Oil.
Apparently in the leather tack/horse community Hydrophane is a well known and trusted product line. This stuff is supposed to be progressive in its effect and permanent once applied. Will start on a backrest first as would rather ruin it then a saddle. This guys knows his leather and support products though. So I'm willing to give it a try based on his advice.