Chemical in rug backing?

[Darthmaeglin]

Cold-water extracted the back of this rug and got an interesting surprise. The originally grey backing shed green, like I was pulling the green out of it. The backing itself now seems to be dirt-brown, but as you can see there's green blotchy stuff all over. It came back pretty quickly after cleaning a section, like it was wicking up from the foundation. It stains real easily (ran my hand through it like a dum-dum...). Also got a pic of some of my wastewater. There is a ton of color in this stuff. Anyone familiar with this kind of stuff? Fire retardant? Kool-Aid?
For reference, the rug is 100% synthetic shag. It had spots of the same green on the front which I documented in advance, but I thought it was spilled Gatorade or something.