Moro beans from Rancho Gordo. A very mild bean, small or medium small. Makes a dark pot liquor. Rancho Gordo’s website describes it as being like a cross between a pinto bean and black bean, and I would agree with that.
Dark exterior, but flesh inside stays light even after cooking. Has a bit of taste, but not real strong. I think it would go very well in chili or stew recipes that have a few dark bitter ingredients, like stews with Irish stouts in them, or a chili with a little bit of cocoa powder.