mud stain vs discoloration

mud stain and discoloration both are nouns.

Word	Noun	Adjective	Verb	Adverb
mud stain	Yes	No	No	No
discoloration	Yes	No	No	No

As nouns, discoloration is a hypernym of mud stain; that is, discoloration is a word with a broader meaning than mud stain:

Other hypernyms of mud stain include discolouration, stain.

mud stain (noun)	discoloration (noun)
a stain produced by mud	the act of changing the natural color of something by making it duller or dingier or unnatural or faded
	a soiled or discolored appearance