Proud owner of one Lunar acre! (Campanus Crater, The Moon)
Don't do it! It will never take the dye the way it did the first time and often makes the saddle look worse. Instead, use leather darkening oil. That will make it look better. The dye is a bad idea. Spirit based dyes are the best for permanently dying leather, but only when it's never been dyed. It will soak up unevenly since it's been dyed and conditioned (and cleaned).
Using water based dyes never works well and a lot of it will come off when you clean the saddle...or on someone's clothes when they ride.
The higher the quality the leather is will not hold the dye. Which is why your albion has turned colors.
Doesn't really matter what brand, better quality leathers will at some point in time will turn colors.
If its the very fine leather that turns greeny/ grey no amount if oiling will change the colour. There are a couple of brands of saddles made of this fine leather that are notorious for going green and nothing works. I know i have a couple. A friend if mine did try to dye hers and completely ruined it as a show saddle. It was not fit to be seen in public. Rather than go back to black it turned a revolting browny green which made it look like a rank slime pond. Dont do it. And dont try to drench it in oil. These fine leathers donot take oil well nor do they change colour with them.
Just tried the Tanners Leather Darkening Oil. I'll know better what it looks like after a day but right away it made my knee rolls extremely darker - almost like new, but not so much the rest of the saddle. The knee rolls are made of a much softer leather than the seat and panels.
When I sold a saddle through Pelham Saddlery they have a cleaning/darkening regime you can have them do. They wouldn't tell me the whole secret but showed before/after pictures and it made a difference. My saddle didn't actually need it, but they were kind of excited about showing off what they could do.
Not sure where/how you plan to sell it but they did a good job with mine.