"The beer is dark."
Translation:La bière est foncée.
An explanation can be found here: https://www.duolingo.com/comment/26961672/fonc%C3%A9-vs-sombre (Quote of the important part below)
"Foncé" is only used for colours, while "sombre" works in any context (including colours, so "une couleur foncée" or "une couleur sombre" mean almost the same. However, if you speak of a specific colour, you must use "foncé", so "du bleu foncé").
"Sombre" can also be used for "not enough light", for example "Lorsque le soleil se couche, il commence à faire sombre."
Not sure if it can be trusted but here's one answer: https://www.reddit.com/r/French/comments/5cxxpb/fonc%C3%A9_vs_sombre/
That's an interesting answer, but it doesn't explain why "sombre" can't be used in this sentence. If the sentence to be translated was "The beer is dark brown," then this would apply, but the word "brown" isn't in the sentence. As someone else mentioned, we've been translating "Le costume est sombre," for a long time now. So why can't "la bière" be "sombre" as well?
from what i've worked out it's just the accepted french translation that implies the same meaning as the english does. (you can describe a beer as dark when describing how it looks but you imply a different meaning to when you ask for a dark beer at a bar) Honestly that could be totally wrong.
Also I believe sombre means dark in general but if you had a dark purple that would be darker than a dark yellow so whilst the blue maybe be sombre the yellow may just be foncee, these are just speculations though
OK we're talking about sombre vs foncé. It's true that foncé would indicate that the "color"of the beer is dark. However, if I mean the beer itself is dark - regardless of the color - it seems that sombre might also be correct. But, I suppose foncée is MORE correct because you most likely mean that the color of the beer is dark.
"Cette bière est trop légère et trop blonde pour moi. Vous avez peut-être une bière forte et foncée?"
"Voilà Monsieur. Je considère que vous aimeriez cette brune."
Le jeune homme s'est assis tout seul au coin lointain du bar ou, sans parler et sans regarder aux autres, il a commençé à boire sa brune solitaire et sombre, perdu parmi ses pensées maussades et bilieuses.
This is just a guess, but could this express the difference between foncé and sombre?
Why 'sombre'can not be used instead of 'fonce' ? As there is no colour describing the subject 'biere", my answer is correct. Because only in the earlier clarification, 'sombre' is used for overall appearance of a subject and 'fonce' is used to enhance the adj. (Colour) of the subject. Pl. Explain.