During the period of 3rd Tae-Jong and 4th Se-Jong, Yi Dynasty has established sound basis for ruling power and aristocratic social cast system. And the regulation for official dress has also been firmly established during the same period. The establishment of KWAN BOK SACK (Office of Hat-Dress) in 16th year of Tae-Jong (1416 A.D.) and the enforcement of KWAN BOK JI JAE (System of Hat and Dress) in 8th year of Se-Jong(1426 A.D) indicates the completion of system of official dress in the dynasty. In this study, the author tried to find out the concept of color in the ruling society since the concept of color in KWAN BOK JI JAE, which is the social reglation in the fendal dynasty, had greatly been influenced by these class of people. Effort has also been given to investigate what motivated the establishment and enforcement of KWAN BOK JI JAE, through the descriptions revealed in SE-JONG SILLOK. It can be concluded in the first that, in KWAN BOK JI JAE no new color concept appeared and its significance only remains on the fact that it establshed the social regulations which were existed before. And secondly, the works of Se-Jong in KWAN BOK JI JAE, in contrast to his magnificance in other fields, only showed great influence of toadyism (Chinese culture).