red herring vs smoked herring

red herring and smoked herring both are nouns.

Word	Noun	Adjective	Verb	Adverb
red herring	Yes	No	No	No
smoked herring	Yes	No	No	No

As nouns, red herring and smoked herring are synonyms defined as:

red herring and smoked herring: a dried and smoked herring having a reddish color

red herring (noun)	smoked herring (noun)
any diversion intended to distract attention from the main issue	a dried and smoked herring having a reddish color
a first draft of a prospectus; must be clearly marked to indicate that parts may be changed in the final prospectus
a dried and smoked herring having a reddish color