With the serrated knife, cut 1″ thick slices of the loofah. Place a slice into the bottom of each well in the mold.
Cut the soap base into 1/2″ cubes and divide into three piles. Place 1/3 of the soap cubes into a microwave-safe measuring cup, and melt in the microwave in 20-30 second increments, stirring well after each microwave session to ensure that the soap is completely melted.Note: You will be filling two wells of the mold with each batch of melted soap.
Add 1 tsp. coconut oil, 5 drops of coconut fragrance oil (if using), and 4-5 drops of pink soap colorant to the melted soap base. Pour half of the pink mixture into one of the wells of the mold. Add 2 drops of purple (or blue) soap colorant to the remaining melted soap, stir, and pour the soap mixture into another well of the mold.
Spritz the top of each soap with isopropyl alcohol to remove any air bubbles.
Repeat the process for the other colors: 1) Add 5 drops of yellow colorant to the melted soap base, stir, and mold half of the mixture. Add 2-3 drops of orange (or pink) colorant to the remaining yellow soap base to make orange; mold. 2) Add 4-5 drops of blue colorant to the melted soap base, stir, and mold half of the mixture. Add 3-4 drops of green (or yellow) to the remaining blue soap base to make green; mold.
Allow the soap to sit undisturbed until completely firm and cool (approximately 60-90 minutes depending on temperature and humidity) before unmolding.