Fashionable color of dresses can be regarded as a certain social phase transition. In this paper a Fokker-Planck equation, is derived to describe these phenomena. The bifurcation processes of deterministic equations which describe dynamical behaviors of subsystems, and the corresponding different probability distribution configurations of Fokker-Planck equation which can be regarded as the random description of bifurcation processes of a social system are studied in.detail. Computational results and its interpretations are presented in the end.