white fox vs blue fox

white fox and blue fox both are nouns.

Word	Noun	Adjective	Verb	Adverb
white fox	Yes	No	No	No
blue fox	Yes	No	No	No

As nouns, blue fox is a hyponym of white fox; that is, blue fox is a word with a more specific, narrower meaning than white fox:

white fox: thickly-furred fox of Arctic regions; brownish in summer and white in winter
blue fox: a variety of Arctic fox having a pale grey winter coat

white fox (noun)	blue fox (noun)
thickly-furred fox of Arctic regions; brownish in summer and white in winter	a variety of Arctic fox having a pale grey winter coat