As the author says: "You might also need colors to emphasize different semantic states" It's a reasonable choice to use them, but you don't necessarily need to

As the author says: "You might also need colors to emphasize different semantic states" It's a reasonable choice to use them, but you don't necessarily need to. It is a useful example for palette building as it is a common choice to us semantic colors, and it helps to demonstrate adding colors with substantially different hues.