Gotchya. There are multiple types of bi-color, some with three contacts. So yes, with three contacts you'd have to use the output for separate red-green-yellow and wire the yellow output lead to both the red and green contacts with diodes in place to protect backfeeding. The internals of a multi-color LED are separate lighting elements, so a tricolor should look no different from a bi-color as long as it's small enough. You could adjust the yellow color by adding resistors to the feed lines for a yellow aspect. Different reisitors on the red and green contacts should result in different color tones.
