whiteness vs skin colour

whiteness and skin colour both are nouns.

Word	Noun	Adjective	Verb	Adverb
whiteness	Yes	No	No	No
skin colour	Yes	No	No	No

As nouns, skin colour is a hypernym of whiteness; that is, skin colour is a word with a broader meaning than whiteness:

Other hypernyms of whiteness include complexion, skin color.

whiteness (noun)	skin colour (noun)
the quality or state of the achromatic color of greatest lightness (bearing the least resemblance to black)	the coloring of a person's face
lightness or fairness of complexion
the state of being unsullied by sin or moral wrong; lacking a knowledge of evil