Duo-R (and all Duo) has only 1 LED for drive activity. I wanted power on LED and I wanted it separate from the existing red LED so I don't get purple glow. Mounting the second LED would have worked but I wanted to leave the exterior looking stock so I had to figure a way to make blue LED come on only when red LED is not on. Simple schematic I found worked: I wired it dead bug style. With total of 4 parts, it wasn't worth wasting pcb. I mounted the LED on top of the transistor so the blue LED would sit about the same height as the red LED. Conveniently the collector and emitter leads of 2n3904 are spaced the same as LED leads so nothing special there. Here's a video of it in work:
