"Their black dress is nice."
Translation:Leur robe noire est jolie.
If the colour is describing a masculin noun, it is 'noir' E.g. Le thé noir
If the colour is describing a feminine noun, it is 'noire' E.g. La robe noir
This applies to all colours...with a few exceptions: Masculine (M) Feminine (F) M=blanc F=blanche M=violet F=violette M=marron F=marron (marron never changes!) M=rose F=rose (if they already end in 'e', they do not change)
Hope I helped! :)
The drop-down menu offers a few possible translations, but it does not clarify context, it does not propose specific translations for the sentence you are working on nor the actual meaning of the words proposed. It is by no means a dictionary and if you want to be more accurate in your learning, I suggest you open another tab open on a good online dictionary, which you can refer to as you go.
For starters, "une robe" is feminine, so we need the feminine form of "beau" which is "belle". (Note: this could also be the result of Duolingo preferring "beau/belle" for describing people, and "joli/jolie" for describing things, but nonetheless, "beau" would still be wrong.)
Furthermore, the conjugations for être are as follows:
Je suis, tu es, il/elle est, nous sommes, vous êtes, ils/elles sont,
As you can see, the proper conjugation of être would be "est" for the sentence "Leur robe noire est belle" or, as Duo seems to want it: "Leur robe noire est jolie."
The thing is, yes, contemporary usage makes the "singular they" correct (and in fact, so does historical usage), but there are a lot of grammar books (written by descriptivists) that will disagree, so it's still going to be a point of argument.
The other thing is that "they" used for one person in English is still grammatically plural, not grammatically singular.
No, because "robe" is a feminine noun. The adjectives are not feminine because the hypothetical owners of this dress are female; they are feminine because the noun "robe" is a feminine noun. If this dress belongs to Bob and Tom, who run a costume shop (or are drag performers, or whatever context you like to give it), it's still "Leur robe noire est jolie."
85% of French adjectives are regular and placed after the noun.
Color adjectives are regular: "leur robe noire est jolie"
A small bunch of adjectives are placed before the noun.
I must be far too old, "geniale" I see here mentioned; I don't think this word even existed when I was born! I would argue that the creator of a stunning dress could be genial....But I know I'd lose the argument, because language is like fashion, very eccentric. Although I'm only here because I was a little off balance with one dress belonging to many. But I realised if you speak of a shop and refer to owners, staff it would be correct to say their (leur)