1. A color information processing method comprising: inputting reference data including color information about each pixel or each pixel group of a reference medium and evaluation target data including color information about each pixel or each pixel group of an evaluation medium by an input means; calculating an evaluation result by a calculation means, for each range corresponding to each ink key which controls an ink amount in the reference medium and the evaluation medium, by comparing the color information items of both the reference data and the evaluation target data about each pixel or each pixel group based on the reference data and the evaluation target data in a specific area which is a unit of evaluation; and adjusting a printing color of a printing machine based on the evaluation result by an image processing means.