Is 'Black' a gradable adjective and 'pink' non gradable?


Could you please tell me if ‘Black’ is a gradable adjective and ‘pink’ non gradable? How do you find the following?

White- whiter- whitest
Black- blacker- blackest
Pink- pinker- pinkest
Blue- bluer- bluest


I’d say that they are theoretically non-gradable, but in reality they are sometimes found in comparative and superlative forms or with adverbs of degree.

For example, a toothpaste company might advertise that “your teeth will be whiter” if you use their toothpaste.

Or if someone’s eye color is a particularly striking shade of blue, you might hear someone say "She has the bluest eyes I’ve ever seen."

Pink and black are probably less likely to be compared, but it might happen:
Her complexion is pinker than his.

"Her cheeks and nose were very pink after being out in the cold for so long."

John is in a black mood. Sam’s mood is even blacker. Jack’s mood is the blackest.