skin color vs colouring

skin color and colouring both are nouns.

Word	Noun	Adjective	Verb	Adverb
skin color	Yes	No	No	No
colouring	Yes	No	No	No

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

skin color: the coloring of a person's face
colouring: a visual attribute of things that results from the light they emit or transmit or reflect

Other hypernyms of skin color include color, coloring, colour.

skin color (noun)	colouring (noun)
the coloring of a person's face	the act or process of changing the color of something
	a visual attribute of things that results from the light they emit or transmit or reflect
	a digestible substance used to give color to food