(Screenshot by Michelle Starr/CNET Australia)
If you can see, you've been trained to recogniseas "yellow" or "blue". But we will probably never know if we all see those colours the same.
My tiny, six-year-old mind was blown the day I pondered what if the colour that looks red to me looks to another person like the colour I recognise as blue?
And then further, when I realised I would never be able to find out. Think about it: we all grow up knowing that a certain frequency of light wave is red. You have no way of seeing through another person's eyes; and therefore, no way to tell that they are seeing that colour differently. And even if they were, they're not going to identify it as blue. It's red.
It all gets very bogged down; but as Michael of Vsauce points out, we do in fact know that some people see colours differently. We call this colour blindness, where the individual can't see certain hues or shades, or a combination of both, and it means that their ability to pick out fine detail may be lower than that of a non-colour-blind person.
So maybe everyone does see colours differently. And taste things differently. And hear things differently. Scientifically, there's probably not a lot that can be done to ascertain whether or not this is so; but it's a great start for some deep philosophical thinking.
Watch the video below, head here for further reading or head here to sign up to the Vsauce YouTube channel.