To analyze color difference into three characteristics is a hard work, because it takes long time to get a required value and this may be the main cause of errors. Being necessary to simplify the method within an allowable error, this paper gives the method using the computer for analysis of colour. In case of analyzing color difference into three characteristics by using computer, errors within down to the first decimal place seem to be unavoidable. But, giving consideration to instrumental errors in measurement, a personal error and errors given by the tedious work in case of using tables and charts, the figures down to the first decimal place seem to be negligible. The use of a newly developed software saves us time and must give us a proper way for analyzing color.