watercolour vs water-base paint

watercolour and water-base paint both are nouns.

Word	Noun	Adjective	Verb	Adverb
watercolour	Yes	No	Yes	No
water-base paint	Yes	No	No	No

As nouns, water-base paint is a hypernym of watercolour; that is, water-base paint is a word with a broader meaning than watercolour:

watercolour: a water-base paint (with water-soluble pigments); used by artists
water-base paint: paint in which water is used as the vehicle

watercolour (noun)	water-base paint (noun)
the art or technique of painting with watercolors	paint in which water is used as the vehicle
a painting produced with watercolors
a water-base paint (with water-soluble pigments); used by artists
water-soluble pigment

watercolour (verb)	water-base paint (verb)
paint with watercolors