Add soap to a microwaveable bowl. Microwave on high for 30 seconds. Microwave an additional 10 seconds. Stir. Continue to microwave in 10 second intervals, stirring in between, until soap is melted.
Stir in soap colorant and essential oil. Pour into a silicone mold.
Let sit for 40 minutes to 1 hour at room temperature until hardened. Remove from silicone mold by gentling pushing on the bottom.