Red Octave differs from the rest in two ways.
1. When you max the gain knob, you get more gain and sustain, not a buzzing fuzz like other octave up boxes.
2. Red Octave adds an additional stage of mild overdrive to round out the sound and make it sweeter. Instead of being overly bright and shrill, Red Octave produces a warmer and more musical octave up effect.
Due to limited supplies, parts may change from batch to batch. Values stay the same but the style/appearance may change.