Whisk dry ingredients together. Add the coconut oil, food coloring and essential oil. Mix until ingredients are well blended (I had a hard time getting this gel coloring to mix in until I added water).
Add 1/2 Tbsp water and mix well. Check to see if the mixture holds together well by squeezing some in your hand. If not, add another 1/2 Tbsp of water.
Fill each side of bath bomb mold with mixture and press to pack it down. Add a bit more of the loose mixture onto each side. Press both sides of mold together tightly. Tap gently on the side of the bowl and twist the mold to release the bath bomb. Carefully set aside to dry.
Let dry for a few hours and place in an airtight container or bag.