Pour equal amounts of red, blue, and green food coloring into a small mixing bowl.
Green Food Coloring, Red Food Coloring, Blue Food Color
Combine the color with black. Use a toothpick to mix.
Test your black by spreading some on a white plate.
It will mostly appear blue or greenish. In that case add a little more red, a drop or so. If it appears too red, add a drop of blue, it appears too purple, add a drop of the green.
Mix and test on your plate until you are satisfied with your black.
When using it in your food, as for example in frosting, add a small quantity to some ingredient that you want to color. Check if it's black enough or if it needs more black. Add more if needed. *See Notes
Store leftovers in a small bottle that you can close or in a small bowl with a cling film over it and keep in your fridge.
Video
Notes
A few drops of black food coloring can be enough to dye your foods pitch black. Start with a few drops and take it from there.The quantity of red vs blue vs green to create black depends on the brand and quality of food coloring that you use. Adjust as needed.Gel colors are more intense. A small quantity goes a long way. Also allow the color to set for 10-15 minutes, that way you will know if you need to add more or not. Gel colors get more intense in time.