1. A reproducible color gamut compression method adapted for a combination of a plurality of display devices that are different in reproducible color gamut, for converting a color not reproducible by a target display device into a reproducible color, comprising the steps of: computing a target reproducible color gamut, based on color reproduction characteristics of the devices, so as to produce reproducible color gamut information; computing a compression ratio used to compress a source reproducible color gamut, based on a reproducible color gamut of the target device and the reproducible color gamut information; acquiring compression method determination information used to determine a method of compressing the source reproducible color gamut; determining a method of compressing the source reproducible color gamut, using the compression method determination information; and converting the source reproducible color gamut into the target reproducible color gamut, using the compression method thus determined.