Please note: I do NOT wish to debate here whether blue light is really harmful or not. I just want to discuss what the anti-blue light technologies actually do.
What I found:
Please note: To avoid any mercantile involvement, I'd rather not give any information that would help identity the manufacturers quoted below.
A lens manufacturer (for glasses) declares they master an anti-blue-violet light (UV & HEV) filtering technology. A multi-layer coating is laid over the lens, reflecting incident blue-violet light. They claim: "the lenses are almost completely clear but have a very faint residual tint". NB: another manufacturer with similar technology qualifies it as "interference filtering".
Another lens manufacturer declares they master an anti-blue-violet "absorptive filtering" technology. They claim: "we have also managed to correct the slight residual yellow tint".
A computer monitor vendor claims their anti-blue light screen achieves "over 90% reduction in eye-damaging blue light with little to no effect on display brightness and color".
What I believe:
Please note: I do have a general physics background but I am not an optics specialist, so I do not claim absolute truth.
a) Blocking 100% intensity in the wavelength band associated to blue color implies those wavelengths cannot make their way to your eyes, which implies you cannot see the color filtered, which implies you see only the yellow/green and red parts of the spectrum, which implies that your color perception is indeed altered: everything will look yellowish to reddish.
b) Moreover, since part of the spectrum of incident light is blocked, then total light intensity is reduced which should result in dimmed light perception (unless, of course, if the source spectrum contains no blue light).
Now regardless of the technology used (reflecting, absorbing, sorcery, voodoo, etc.) and even if only 90% or 50% or whatever intensity is blocked, the effect will be lessened but still, color perception will be altered and everything should look less blue and more yellow-red. And unless intensity loss is compensated (e.g. monitor brightness tuning), it should still make things look dimmer.
So regarding claims in 2) and 3), I am skeptic. What do you think? Any insights are welcome and especially from people with advanced knowledge of optics or color theory.