Unno, I can’t see much use for blue. Red and green are most used for night-vision, IR same ’though with IR-registering scopes (btw, you can judge its IR performance by using your cellphone as a video-camera, even if it’s not recording, and seeing how it lights up things).
Blue might get some things to fluoresce, but then I’d rather have a real UV module (385nm at the very least, preferably 365nm). Blue is the hardest light to see, or even for your eyes to focus on (everything looks blurry). A blue module might be a novelty, just not terribly useful.
