Black beans are a natural way to create blue dye for your textile and craft projects by using a cold process. Are you soaking black beans for a pot of soup? Fantastic - just let them soak an extra day and the thick leftover water can be saved for a blue that can have hints of green, purple and gray. This tutorial will show you how to create a 'cold brew' for a lovely blue dye, as well as the resulting color swatch samples (cotton & silk) with various mordants.