I think this tweet explains the concept pretty intuitively.
To make it more explicit, you could record a GIF placing the two gradients: pure red () & pure green ().
Tell them that red is “man”, green is “woman”, & blue is “attack helicopter” or “dog”, then demonstrate the huge “number” of values between red & green by color-picking random spots on the canvas. Challenge them to find a spot on the canvas has even a smidgen of blue.
Explain the perception of a gender binary by saying most colors are approximately red or approximately green, yet there is still a spectrum of in-between values impossible to succinctly enumerate.
If they genuinely have further questions, it’ll be a good opportunity to teach. If not, they’re probably deliberately trying to misunderstand.
