I used your idea of reflecting the light back towards the other side, and it let me make this!
why are you chaining shifters? Don't you lose 10% efficiency each time, and gain nothing by having it pass through 3 shifters?
You technically gain more, as each time it passes through the shifter it converts more light. So by chaining 3 together you convert all light, including blue, negating the 10% efficiency loss.