[thefro526]

Originally Posted by MagiChau

You could wave up giant colored stick(s) in the air, everyone will see that.

Once there are tubes on the top row of pegs, signs become a lot more difficult to see.

We're using three different LED patterns to indicated tubes to our Human Player. They're each wired to their own spike and use both the M+ and M- terminals. We were fortunate enough to have the weight and space for three spikes so this was the easiest solution for us - but if we did it again, we would probably use two spikes and have the LEDs ground to the PD.