It’s just the concept of additive color mixing vs subtractive color mixing.

Adding pigments together will ultimately create black. While adding more light together will ultimately make white.

With pigments you’re taking away from the color space. You paint red to subdue all other colors except for red.

But you use red light to make sure red is better seen.

https://www.yubico.com/

I use it as my 2nd facor authentication.

Bitwarden with YubiKey

I’m assuming they’re plain text. There’s is no perceivable way they can only use those data points to to figure out which hash it is. Unless of course they’re using their own “hashing” function which isn’t secure at all since it’s probably reversible.