Great Britain vs green paper

Great Britain and green paper both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
green paper	Yes	No	No	No

Great Britain (noun)	green paper (noun)
an island comprising England and Scotland and Wales	a preliminary report of government proposals that is published in order to stimulate discussion
a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom