You'll get a better response posting on the French language forum rather than the generic Duolingo forum.

the "e" in noir is for feminine. Ex: La chienne noire (The black dog (female dog)). No "e" when masculin. Ex: Le chien noir. (male dog)) Hope this helps. :) Befriend me if you'd like, I am native french and can help you when you need it.

you use noir with "e" when the noun is female