The girl says that the number 20 has a colour that is a mix of the colours of 20's factors. I find this interesting, because I always thought arithmetic is imaginary, right? If she didn't learn basic arithmetic, would 20 have had the same colour? Or would 20 have the same colour, but to her, the colour would seem random to her?
Interesting, I have synesthesia, but it's just a direct correspondence between each letter/digit and a color. So 20 has the color of 2 and then the color of 0.
Do you physically see the colors superimposed on the numerals out in the real world? Is it a visual experience?