You cannot measure perception with a color picker. Eyes + brain is not a measurement instrument.

Just like you cannot measure amount of salt used in a dish with your tongue.

Nope. Color cannot be measured, it is created in the brain. Pickers show pixel values (stimulus) and often don’t correlate to the experienced color.

Incorrect. It is impossible to deduce the “real” color from the photo, both sets are true.

The photo is simply bistable.

You can argue that “the real dress bla bla bla”, but nobody’s looking at the real dress and everyone’s looking at the photo.

Color is created in the brain, not in the pixel values. Pixel values often have no correlation to the color that’s produced in the brain.