I can't say for sure what the color is, but I doubt you "scorched" the citrate. Trisodium citrate melts at 300 C / 570 F and decomposes at temps even higher than that.
It's more likely the color is from trace impurities from your pan or the original ingredients -- I assume that would be baking soda, citric acid and water, right?
None of the ingredients the average soap maker would use to make sodium citrate will be the extra pure chemicals you'd get in a chemical lab. Any impurities in your ingredients will become more concentrated when you evaporate the water.