An apparatus for deciding representative colours of a colour image, comprising: a grouping device for dividing pixels, which construct a colour image represented by applied colour image data, into a plurality of groups in a L*a*b* colour space in such a manner that pixels at positions close to one another in colour space will belong to the same group and wherein said grouping device divides the pixels into a plurality of clusters (g1-g6), such that each cluster is encompassed by a circle and wherein the circles have the same size, to which pixels for which the positions of the colour thereof in colour space are close together belong; a representative candidate colour deciding device for deciding as a representative candidate colour, group by group, one colour among the colours belonging to each group of the plurality of groups divided by said grouping device, wherein the centroid of each group is calculated and a colour indicated by the position of the calculated centroid is decided upon as the representative candidate colour of the group; and a representative colour deciding device for deciding that, from among a plurality of representative candidate colours decided group by group by said representative candidate colour deciding device, the colours of a plurality of pixels present at a position remote from the position of grey in this colour space are the representative colours of the colour image, wherein the origin in the a*b* plane indicates grey, wherein the representative colour deciding device comprises: a first score calculating device for calculating a distance score, in said colour space, between a representative candidate colour that has been decided for every group by said representative candidate colour deciding device and grey, wherein grey is the origin of the a*b* plane; and a second score calculating device for calculating a score representing the number of pixels in each cluster (g1-g6); a final score calculating device for calculating a final score group by group from the first and second scores that have been calculated; wherein said representative colour deciding device decides the representative colours of the colour image based upon the representative candidate colours that provide the three highest final scores among the final scores. a grouping device for dividing pixels, which construct a colour image represented by applied colour image data, into a plurality of groups in a L*a*b* colour space in such a manner that pixels at positions close to one another in colour space will belong to the same group and wherein said grouping device divides the pixels into a plurality of clusters (g1-g6), such that each cluster is encompassed by a circle and wherein the circles have the same size, to which pixels for which the positions of the colour thereof in colour space are close together belong; a representative candidate colour deciding device for deciding as a representative candidate colour, group by group, one colour among the colours belonging to each group of the plurality of groups divided by said grouping device, wherein the centroid of each group is calculated and a colour indicated by the position of the calculated centroid is decided upon as the representative candidate colour of the group; and a representative colour deciding device for deciding that, from among a plurality of representative candidate colours decided group by group by said representative candidate colour deciding device, the colours of a plurality of pixels present at a position remote from the position of grey in this colour space are the representative colours of the colour image, wherein the origin in the a*b* plane indicates grey, wherein the representative colour deciding device comprises: a first score calculating device for calculating a distance score, in said colour space, between a representative candidate colour that has been decided for every group by said representative candidate colour deciding device and grey, wherein grey is the origin of the a*b* plane; and a second score calculating device for calculating a score representing the number of pixels in each cluster (g1-g6); a first score calculating device for calculating a distance score, in said colour space, between a representative candidate colour that has been decided for every group by said representative candidate colour deciding device and grey, wherein grey is the origin of the a*b* plane; and a second score calculating device for calculating a score representing the number of pixels in each cluster (g1-g6); a final score calculating device for calculating a final score group by group from the first and second scores that have been calculated; wherein said representative colour deciding device decides the representative colours of the colour image based upon the representative candidate colours that provide the three highest final scores among the final scores.