The example I sighted uses Une tenue (not une chemise) and the correct answer was given as:
une tenue bleu marine.
Bleu marine is correct. It is an invariable compound adjective. (It does not derive from the word 'marin' but from 'marine' directly).
To supplement Maarten's answer, here are 2 examples below:
Un pull bleu marine = a navy blue jumper/sweater
Une serviette de bain bleu marine = a navy blue bath towel
Trois vestes bleu marine = three navy blue jackets
I hope this is helpful.
Bonne journée !
Sign in to submit your answer
Don't have an account yet? Join today
Test your French to the CEFR standard