On the origin of color anom On the origin of color anom aly between multiple imag aly between multiple imag es of lensed quasars es of lensed quasars Atsunori Yonehara Atsunori Yonehara (Univ. Tokyo, Inoue Fell (Univ. Tokyo, Inoue Fell ow) ow) Hiroyuki Hirashita (SISSA) Hiroyuki Hirashita (SISSA) Philipp Richter (Bonn Uni Philipp Richter (Bonn Uni v.) v.) Atsunori Yonehara