For me the best to do is pour of how many colors I want and dump the full amount in the balance of the batter. My other method is to pour 3 leave one un fragranced and pour a little of each remainder then add the balance to the largest amount of batter. If you are only using enough to fragrance 1/4 of the soap, I would not bother fragrancing at all. But we like strong fragrance as do my customers, and I deal with several very discoloring fo's. If you use the method of varying the fo it is always a surprise when it cures, because you cannot tell with the batter. If you want swirls you can pour off and use bright colors such as yellows, pinks, purples, bright green etc add not fo, and pour the fo in the balance of the batter.