In designing a Web page, background color coordination is important because it has the strong impact on the impression of the page. Generally, background color combination is decided depending on designer?s sensibility, experience or knowledge. However, it is not easy for a Web page designer to decide appropriate color combination for a specific Web page impression. Additionally, it is quite likely that the impression affected by the color combination that the designer intends is different from that actually a person who sees the Web page. This paper introduces a system that supports to decide appropriate color combination of a Web page for intended impression. For this purpose, first we analyzed the result of the image assessment of 216³ different color coordination. Then, we developed a prototyping system that can support background color coordination for Web pages by using the results of the analysis.