Use black food coloring if available
Mix equal parts red, blue, and green food coloring
Add a tiny amount of brown food coloring to deepen the shade
Use more blue and red than yellow for a darker result
Start with small amounts and adjust gradually
Mix thoroughly until the color is uniform
Let the mixture sit for a few minutes to develop the full color
Add a small amount of black cocoa or activated charcoal only if food-safe and appropriate for your recipe