Also, I wonder how that works if you’re colorblind?

This was probably a joke but I can actually answer that for you.

First of all, afaik there is no scientific consensus that people see the colours the same way. In fact, we most likely don't. The visual colour interpretation is mostly likely merely added on by our brains basing on the knowledge of wavelengths. In other words, there is no such thing as "absolute blue". There is "a blue" which is the colour each one of us' brains was taught to call blue by simply showing the sky. If I were to look through your brain (but not through your eyes, eyes understand wavelengths), we would probably disagree on each and every colour.

Second of all, there are different kinds of colour blindness. It is in fact an umbrella term for different disabilities. My understanding is that they usually involve a spectrum between two hues. So most colourblind will simply be unable to tell a difference between objects of two colours: for example red and green. They see them as slightly different versions of the same colour. However it would be wrong to say that the person in question sees red as green or vice versa, because, again, there are no "absolute colours". Their eyes cannot distinguish between these two ranges of wavelengths and the brain interprets them as the same colour.

And finally, colourblind people, when diagnosed, are fully aware of being colourblind, and furthermore, they DO NOT see in black and white. Even if a person cannot distinguish red and orange, then they still are aware there is a difference that most people around can tell and that there are concepts and feelings associated with them.

What I am trying to say is that a colour-blind person would probably still be able to, for example, associate "red" videos with action and blood, and "green" ones with nature and calmness, even though this distinction is not palpable to them.

Either way, this filtering with thumbnail colour is fucking stupid.