Asklemmy

The simple version is that color blindness is caused by a physical problem with your eyes. If you don't have the parts required to detect certain colors then no glasses are going to fix that. They're just tinted glasses, the guy in the video tries three different pairs from different companies and all they do is tint the world a hideous shade of pink/magenta.

As someone else said above, what they can do is change your ability to differentiate between objects of slightly different colors. You might have a really hard time telling the difference between red and green, but find it easier to tell the difference between hideous vaguely reddish magenta and hideous vaguely greenish magenta. They don't grant you a greater range of color vision, but they do change what color is actually hitting your eyes. Mostly into hideous magenta.

FWIW the guy in the video points out that in his experience it generally made colors harder, not easier, to differentiate.

Main idea: They can't restore any color by filtering or let you perceive any new colors as their marketing likes to claim. At best they might be able to improve contrast of certain colors while reducing contrast for others - which is not at all what they say it does

The video goes much more into depth about their deceptive marketing and such