For the original project, I used two strands of lights, and the code was pretty simple. When you add a third (or more) strand, you need a different approach. To demonstrate this, I built a project ...

// what it does: an arduino program which renders colors to rgb-based light emitting diodes in random fashion to mimic christmas twinkle lights. // EACH LED CAN RENDER ONE OF 6 COLORS: RED, GREEN, ...

With the code written, [Rodrigo] then had to put the hardware together. He stripped down a basic emergency light to get an array of white LEDs and a handy enclosure.