food colour vs food colouring

food colour and food colouring both are nouns.

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

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

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

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

food colour (noun)	food colouring (noun)
a digestible substance used to give color to food	a digestible substance used to give color to food