A color identifying apparatus for identifying the color of a reaction surface which has caused a color reaction with a gas to be specified, includes a reference data storage that stores a plurality of associated sets of reference color information represented by the difference between one and the remaining other two of signal intensities of R, G, B signals of RGB bitmap images of a reaction surface which has caused a color reaction with a gas, and identifying information for identifying the reaction surface, an image capturing unit for capturing an image of the reaction surface and generating RGB bitmap images of the reaction surface, an arithmetic unit for generating color information represented by the difference between one and the remaining other two signal intensities of R, G, B signals from the RGB bitmap images generated by the image capturing unit, and an output unit for outputting the identifying information.