This symmetric solution uses a pair of 2-bit counters. The gear part is used to cause the counters to skip one step, so they count to 3 instead of 4. Because the counters are mirror images, the right one counts up and the left one counts down.
By starting the right counter at 1 and dropping from the right side first, we drop 2 reds then alternately drop 3 balls from each side until they are all used up.
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