skin colour vs colouring

skin colour and colouring both are nouns.

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

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

skin colour: 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 colour include color, coloring, colour.

skin colour (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