Popular Mechanics reports that purple is a “pigment of your imagination”: The human eye doesn’t actually see purple.

This helps your child learn that colours are labels that describe ... It’s not just red, it’s a teddy that’s red. The colour name is secondary to what the thing actually is.

In addition, colours are used to signal things: red means stop where green ... The Colourblocks learn how to sort things by colour and use colour to make patterns. Colours have an order too.