Pink is one of the extra fun ones. You'll notice that there is no pink in a rainbow, but most all the other colors are there. Even showing things like a bit of all the indigo and purples and blues and oranges as it blends from one bigger color to the next. It's all by reading electromagnetic wave lengths of reflected light and the brain processing it and assigning a color to it. This also means that there's no way to prove that the color you perceive as being blue, for instance, is the same color as what anyone else sees as blue. Your brains version of what blue looks like may be completely different.

But pink. Pink is it's own set of weird. At no point across the visible spectrum of light is there a wavelength size that is pink. The longest visible waves of light are red and it works its way down to shorter and shorter waves until it gets to violet.

So what is pink? An imaginary color your mind made up when it receives wavelengths of the longest area of color (the reds) and the shortest (the violets/purples) at the same time. That's pink. There is no real way for your mind to mix those wavelengths to make any known color, so your mind just says "fuck it" and made one so it could interpret that nonsense.