eye color vs colouring

eye color and colouring both are nouns.

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

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

eye color: The pigmentation of the eye's iris.
colouring: a visual attribute of things that results from the light they emit or transmit or reflect

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

eye color (noun)	colouring (noun)
The pigmentation of the eye's iris.	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