mottle vs stipple

mottle is a noun but stipple is not a noun.

Word	Noun	Adjective	Verb	Adverb
mottle	Yes	No	Yes	No
stipple	No	No	Yes	No

As verbs, stipple is a hyponym of mottle; that is, stipple is a word with a more specific, narrower meaning than mottle:

Other hyponyms of mottle include harlequin, speckle.

mottle (noun)	stipple (noun)
an irregular arrangement of patches of color

mottle (verb)	stipple (verb)
colour with streaks or blotches of different shades	produce a mottled effect
mark with spots or blotches of different color or shades of color as if stained	engrave by means of dots and flicks
	make by small short touches that together produce an even or softly graded shadow, as in paint or ink
	apply (paint) in small dots or strokes