We have demonstrated the simple preparation of structurally colored composite films by stacking alternating Os and PB
layers. Os has a much higher refractive index than PB, which causes the strong reflection at the interface between these
two materials. Strong reflection colors were observed because of the interference between the multi-layers. Active
control of the reflection peaks was achieved by swelling the PB layers. From these results, we conclude that black thin
layers enhance the reflection of structural colors.