achromatic colour vs coloring

achromatic colour and coloring both are nouns.

Word	Noun	Adjective	Verb	Adverb
achromatic colour	Yes	No	No	No
coloring	Yes	No	No	No

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

achromatic colour: a color lacking hue; white or grey or black
coloring: a visual attribute of things that results from the light they emit or transmit or reflect

Other hypernyms of achromatic colour include color, colour, colouring.

achromatic colour (noun)	coloring (noun)
a color lacking hue; white or grey or black	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