At least the first article talks about ultra-violet blue, a wavelength out beyond the end of what humans can typically see. If you look at it you'll see that the clothes we wear may actually be glowing blue if we don't take certain precautions to avoid it. Of course, at the end, they sell a product which "helps" with that. I usually take sales pitches with a grain of salt. But heck, I'd rather miss an opportunity due to a deer seeing me than blow the end off the barrel - or worse.
There really is nothing like watching a fellow miss an opportunity virtually in his lap due to a fouled barrel/chamber/bolt to realize the value of a simple piece of tape over the muzzle. Who cares what color it is. Use orange for all I care if you are a felon and want to try to hide the fact that you are carrying a rifle.
Sometimes, the air you 'let in'matters less than the air you 'let out'.
