colour in vs pigment

colour in is not a noun while pigment is a noun.

Word	Noun	Adjective	Verb	Adverb
colour in	No	No	Yes	No
pigment	Yes	No	Yes	No

As verbs, pigment is a hyponym of colour in; that is, pigment is a word with a more specific, narrower meaning than colour in:

colour in (noun)	pigment (noun)
	a substance used as a coating to protect or decorate a surface (especially a mixture of pigment suspended in a liquid); dries to form a hard coating
	dry coloring material (especially a powder to be mixed with a liquid to produce paint, etc.)
	any substance whose presence in plant or animal tissues produces a characteristic color

colour in (verb)	pigment (verb)
add color to	color or dye with a pigment
	acquire pigment; become colored or imbued