complexion vs skin colour

complexion and skin colour both are nouns.

Word	Noun	Adjective	Verb	Adverb
complexion	Yes	No	Yes	No
skin colour	Yes	No	No	No

As nouns, complexion and skin colour are synonyms defined as:

Other synonyms of complexion include skin color.

complexion (noun)	skin colour (noun)
the coloring of a person's face	the coloring of a person's face
(obsolete) a combination of elements (of dryness and warmth or of the four humors) that was once believed to determine a person's health and temperament
texture and appearance of the skin of the face
a point of view or general attitude or inclination
a combination that results from coupling or interlinking

complexion (verb)	skin colour (verb)
give a certain color to