1. Why aren't black eyes "black eyes"?

Black eyes
black eyes ×
"Black eyes" are not all pure black, but the color is very dark, so it should be said:
dark eyes
Black eyes are drops like this
"Dark eyes" or "dark circles" after injury
-i got bad black eye cause he punched me on my face.
He punched me in the face, and my eyes turned black.
-how do i get rid of these black eyes?
How do you get to the dark circles?
2. Why isn't yellow hair yellow hair?
Yellow, black, and white hair is most likely to be wrong. First of all, we must have a correct understanding of the three colors of yellow, white, and black. Are you sure you want to express "yellow hair" like this?
Yellow hair: Refers to the golden pure yellow, it seems that it is rare to see a person's color in life, like a character in an anime.
What we usually call "yellow hair" actually refers to "golden", it should be said:
blond hair: (American notation)
blonde hair (English notation)
Be careful to distinguish from brown hair
Brown hair: Brown hair
Black hair: Also pure black, like Grandma's head is white, she will dye her hair pure black.
Dark black hair, our Asian people's natural hair is rarely pure black but:
Dark hair: Black hair
White hair: Snowflake white, pure white.
Gray hair:
gray hair (American)
grey hair (written in English)
3) Yellow jokes are not yellow jokes
Yellow jokes, here yellow does not refer to yellow color, but refers to "vulgar", so "yellow joke" should say:
yellow joke×
dirty joke