Chop the soap base into smaller pieces and weigh into 1 1/2 pound batches. Place each batch into a microwave safe bowl or large glass mixing cup. Add red pigment and 1/2 tbs of orange peel to one and yellow pigment with 1 1/2 tbs of the ground peel to the other.
Microwave the batch you prefer for the outer stripes for 40 seconds, stir and repeat in 10-20 second intervals just until the soap is melted. Remove and gently stir until the pigment distributes fully and the color enrichens. It will not seem like enough pigment at first, give it time to develop.
Once color is rich enough for your satisfaction add half to bottom of loaf pan and set aside to cool until a firm skin has developed on the top.
While that layer is cooling: Prepare the other batch of soap mixture in the same manner as above. Once fully developed, pour over the first layer. Once again allow to cool until a firm layer has developed on top of soap.
Reheat the remaining soap for last layer, just enough to be pourable (you may wish to add a few more drops of oil as fragrance will dissipate a little). Pour final layer, then allow soap to fully cool.
Once completely cooled soap will be firm. Remove from mold and slice into 3/4″ to 1 inch wide bars. Store in air-tight packaging or containers for gifting or until ready to use.