I work in this industry everyday and have for 20 years we have used some strange things to help match colors. The main point is it cannot have any moisture in it at all we use a lot of powder and have a small cup of plastic mixing it into with a blender or in our in our case a milkshake stir. You can buy Iron Oxide which is rust and it makes a great colorant , we have use Powdered Coco mix like for hot choc. , we have use oil based food coloring. The limits are plenty..