Place the sugar into a small bowl and then add the food coloring. Whisk until the food coloring is distributed throughout the sugar.
Spread onto a baking sheet to dry.
Once dyed sugar is dry, add it to a loaf pan to coat the bottom. Reserving a little for the top if desired.
Cut the soap base into small pieces and place it into a microwave safe dish. Microwave on high 30 seconds, stir and microwave another 30 seconds. Keep repeating the microwave and stirring until the soap base is melted.
Add the colorant and scent to the melted soap base if desired. Stir to combine.
Pour the soap base over the dyed sugar. Sprinkle the reserved sugar on top right way before the soap starts to set.
Let the soap sit until cooled and firm.
Using a knife cut around the edges of the soap loaf.
Use a spatula to gently lift the soap from the pan.
Place on a cutting board and cut into squares.