In a bowl, combine the dry ingredients and stir well. Then divide evenly into 3 smaller bowls.
Pour 1 tablespoon melted coconut oil in a cup and add 2–3 drops of food coloring. Stir well. You won't really be able to see the final color until its mixed with the dry ingredients, so just use your best guess. Add approximately 1/3 teaspoon almond oil (eyeballing it is fine!) and 5 drops of the essential oil of your choice into the melted coconut oil. Mix this well with a spoon.
Pour the coconut oil mixture into one of the bowls of dry ingredients. Use your hands to mix it all together, breaking apart chunks as you go. If you would like to adjust the color, melt a little bit more coconut oil and stir in the dye, then pour it into your bath bomb mixture and continue mixing.
For the two remaining bowls, repeat the process using different food coloring or essential oils, if desired.
Pack the mixtures into whatever mold you like (I used bath bomb molds I found on Amazon—see Notes for the link), layering the colors on top of each other and along the sides of the mold. Pack each side until overflowing, and squeeze both halves together to close.
Freeze for 20 minutes. To remove the bath bomb from the mold, warm the sides of the mold with your hands (this will help melt the coconut oil) until the bomb pops out. Dust with a small pinch of mica for a little shimmer.