Color reaction of picric acid with acetone in an aqueous alkaline solution under the Janovsky conditions was investigated. Two main coloring matters responsible for the observed colors were prepared separately and their chemical structures were determined as a Meisenheimer compound (I-2Na) and a bicyclic compound (II-Na), respectively, as shown in Chart 2 and 3. The correlation between the coloring matters and their roles in the reaction were discussed by comparing the spectral behavior of them with the spectral changes of the reaction mixture.