I discovered through some online research that a 4:1 MUX can be constructed out of three 2:1 MUXs. Nice!
Now, the output doesn't need a logic inverter (NOT gate) because the inverting MUXs are cascaded together.
Be sure to check out the circuit I did, which explains in more detail how I hacked a Binary to 7-segment Decoder into a MUX. https://everycircuit.com/circuit/4846082110259200
Left logic sources: Data In
Top logic sources: Selection
RGB LED: Output
1:4 DEMUX https://everycircuit.com/circuit/6625304558436352 and https://everycircuit.com/circuit/6396779649826816
8:1 MUX https://everycircuit.com/circuit/6477782263267328
16:1 MUX https://everycircuit.com/circuit/6080373636988928
