This is a very roundabout way to make a RBRB/BRBR etc. pattern.
It all revolves around the friction in the gear bits, so this one is only possible if you have a real set. I have already done most of the work: you only need to make the with ramps (but you can also use other pieces to make it fancier).
To trigger this, first choose Red or Blue, and trigger. After that, trigger the other one and it should just go until the balls have run out.
The first step is here:
Remember: only physical sets will work because of the friction.