Wow, I'm impressed with their light output. I got a twin pack that comes with a white LED front and a red LED rear. I run the rear in blink mode and the front as well, but last night I decided to set the front on steady mode. I was surprised by the light it cast in front of me. Small sucker with such output.
Anyhow, do Knogs come in other LED colors? I was thinking of getting blue and putting two in the rear, sorta like police motocycles. Is that illegal? Haha, would be cool though.
I could not resist looking these up since I had no idea what they are here is a pic for those similarly intrigued by their name. They look like a cool idea, but really I would not put them up against a dedicated bikelight (assuming that I found the correct item you were posting about), good to be seen though I'm sure. As for using blue as a headlight I doubt it is legal (but that is a local law thing and I am not a lawyer). Did you want to use blue to preserve night vision or was there another reason? I did some reading here and it looks like blue is the most sensitive, but gives the lowest resolution (vs red or green) due to the distribution of receptors in the eye, and their low number.