I think the surprising part of pink is that it's not physical. Green can be mapped to a single wavelength of a photon. Pink cannot be mapped to any wavelength and is only the combination.

More precisely, wavelength is 2-dimensional but most people see color as 3-dimensional. Our brain invented that extra dimension out of utility. Some people can even see color in 4-dimensions (1).

This happens with physical sensations as well. A few examples (may cause some discomfort):

• You can always see at least part of your nose
• You have to breathe manually now.
• Your tongue can never quite find a comfortable place to rest in your mouth

1. https://www.popsci.com/article/science/woman-sees-100-times-more-colors-average-person