Pigments/paint really is different. I watched a guy preparing white paint to spray a white car. He started with what looked like white to me and then added red and blue. He spayed samples until his spectroscope told him that he had the correct “white”.
White is in quotes because it can vary so much.
Many years ago I was having some custom made gray paint mixed at the store. They had a computerized dispensing system that figured out just the right amounts of different pigments needed. The guy at the counter remarked that there was always at least one shot of a pigment that would surprise the customer. In this case, it was a short blast of a bright green pigment.
It is all about contrast. When you view a printed page indoors, the white paper is darker than the black ink viewed in full sunlight. I highly recommend going to the Exploratorium in San Francisco if you don’t believe this or don’t understand it.
As a slight aside, Vantablack is the blackest substance ever made, absorbing 99.96% of light.
As another aside, even ‘black’ is a construct of the brain. Without any external light input, the thermal noise of your retina and even the random activation of neurons in the CNS produces a background level of visual stimulus. “Eigengrau” is the classical term for the background sort-of-dark-grey color that you see with closed eyes in the dark. It takes the presence of contrast between light and dark for the brain to construct ‘black’ and make it seem darker than eigengrau. It’s why you can see black on a TV image even though the unpowered screen isn’t black.