It's not Armorall, sewage, dumping, or blue balls. Just some kind of reaction between the rubber compound and mud. We leave "blue dirt" in our tractor sheds all of the time. When the mud cakes up on the tires and you park it for a week, come back and it has dried and fallen off the tire, the dirt that was against the tire has a blue tint. Same thing with my 4 wheelers. Leaves blue dirt in the garage all of the time from the tires no matter what kind of mud gets on them.
By the way, I don't armorall my 4 wheelers' or tractors' tires.
