Is this at all the same as what the Wii did in some party games? I vaguely recall years ago at someone's house we played a trivia game of some kind where each team would wear different glasses, so that one team couldn't see (or at least understand) the other's info.
The particular concept shown in the post wouldn't really work with glasses, because you need perfect alignment. It's actually irrelevant that they're different colors.
I don't know what those glasses actually look like, but the general idea is probably similar. You present lots of information and filter out the noise.
With glasses, you can do that via color-tint, polarised light or by having them block out every other frame. These tricks are commonly used in 3D glasses, too, as you need different information on each eye...
What am I missing here? Some kind of steganography?
The patterns are identical, except for where the A is. So, when you overlay the black pattern perfectly, it mostly hides the red pattern.
And then where the A is, the red pattern is colored in such a way that it fills in the gaps of the black pattern, leading to a solidly colored area there.