Intuitive explanation for key exchange with public/private keys
I like it, but it only shows the use of 1 secret key, there's no concept of public key.

The exchanged &quot;mixed colors&quot; are the public keys in the scheme.

Also, color may not be as intuitive as I like because people tend to think you can unmix (even if we made the hypothesis we can't.) And a real-world experiment would probably get messy.

Sorry, but you will have to make some assumptions when performing analogies. And a real world experiment seems useless; if people don't get above analogy then they won't be able to understand key agreement.

Is there another example that would relay on 2 elements from each sides?

If you are relying on an audience that needs to perform work with their bare hands to understand an idea, then you've already lost, as they won't get analogies either. Some abstract thinking is required.