Blueprint - 1x1 3-layers mixer

A 1x1 color mixer with input on the sides (left and right) and output to the front. Works fine with 1, 2 or 3 layers belts, and the output matches the layers of the input (e.g. if you provide a 2-layers belt on both side, you will get a 2-layers belt as an output). No waste, all ratios respected.