A noun - as in a tin of paint. A verb - as in to cover the surface of something with paint.
The word painted is a verb. It is the past tense of paint.
It is a noun as in canvass you paint on. It is a verb as in to canvass someone for a vote.
The word painting can be a noun as in a piece of art. It can also be a verb where it is the present participle of paint.
It depends... If you mean to paint as in "Paint a picture", paint is a verb because it shows action. But if you mean paint as in the literal painting material, then paint is used as a noun because it's a "thing".
part of speech
The part of speech for this particular word is a noun.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "explicit" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "unfamiliar" is an adjective.