food color vs food colouring

food color and food colouring both are nouns.

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

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

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

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

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