It's already in your cabinet. Hydrogen peroxide.
Kaiser had a big orangey-yellow stain (looked like something wet and rusty dripped on him outside) that wasn't coming out with soap and water. I went to Petsmart and bought spot remover for white dogs, paid 9 dollars, did nothing! Finally tried peroxide and it came right out, no rinsing.
Here's hoping to save you 9 dollars!
Candace
I use peroxide to clean up the post birthing goo and yuck all over my dams coats....usually shades of red and green...it does very well and buys me a few days until I can get their back ends in the tub to tiddy them up...:)