Bonjour Jillian,

Here "atlantique" is an adjective referring to a proper noun/name (i.e the Altantic being the ocean). "D' Azur" means "de couleur bleue" and was invented by a French writer, Stéphen Liégeard, in 1887. He was originally from "la Côte d'Or" department and used the same name structure to substitute the azure colour of the Mediterranean. 

See here for more details: https://en.wikipedia.org/wiki/French_Riviera

I hope this is helpful.

Bonne journée !

Bonjour Maeve,

I have amended my previous reply.

I hope this is clearer.

Bonne journée !