redden vs color in

redden and color in both are verbs.

Word	Noun	Adjective	Verb	Adverb
redden	No	No	Yes	No
color in	No	No	Yes	No

As verbs, color in is a hypernym of redden; that is, color in is a word with a broader meaning than redden:

Other hypernyms of redden include color, colorise, colorize, colour, colour in, colourise, colourize.

redden (verb)	color in (verb)
turn red, as if in embarrassment or shame	add color to
turn red or redder
make red