colouring vs food color

colouring and food color both are nouns.

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

As nouns, colouring and food color are synonyms defined as:

colouring and food color: a digestible substance used to give color to food

Other synonyms of colouring include coloring, food coloring, food colour, food colouring.

colouring (noun)	food color (noun)
the act or process of changing the color of something	a digestible substance used to give color to food
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