"The colors of the club are blue and black."
Translation:Die Farben des Vereins sind blau und schwarz.
You've got a point, and I had to look this up: both can be used.
According to the Duden (dictionary) website: "Die bevorzugte Farbe seiner Bilder ist blau/Blau." "The preferred colour of his paintings is blue." - and - "Ihre Lieblingsfarbe ist grün/Grün." "Her favourite colour is green."
I suspect it hasn't always been like this (cf. the spelling reform of 1996 and its ongoing reforms), and personally I would have suspected you need to capitalise colours in this context. In "Das Kleid ist grün" the colour is, of course, an adjective that describes the dress itself, but in "Her favourite colour is green" the colour stands for itself, if you know what I mean. It's not "a green-coloured colour" as it is "a green-coloured dress". But if Duden says you can use both, we can't argue with that...
Shouldn't "Vereinsfarben" for "club colors" work here? "Die Vereinsfarben sind blau und schwarz." https://www.linguee.com/english-german/translation/club+colors.html
No no no, die Farben vom Club sind rot und schwarz!!
Sorry, couldn't resist. :) "Der Club" = specifically the 1.FCN (Nuremberg football club). Seriously, though: When talking about a sports club, you do say "Verein" and not "Club".
A tennis club can be both, a poker club or chess club could probably be both, a reading club or night club would be a "Club". So it depends on the context. It's better, though, to say "des Clubs" instead of "vom Club" (except when you're talking about the FCN ;-) ).
Germany has this historical tradition of "Vereine". A Verein has statutes, "e.V." is short for "eingetragener Verein" = one that is officially listed in a register. A "Club" has more connotations of members who are close to each other (weekly gatherings to play bridge or learn a language, golf club), a "Verein" more of promoting a certain issue (sports, rabbit breeding, gardening, preserving the historical city centre) in a more organised way.
"Den" can serve as the article for Akkusativ, masculine. Example: I saw the man. - Ich habe DEN Mann gesehen.
"Den" is also the article used for Dativ in the plural form. For example: The man follows the friends. - Der Mann folgt ("folgen" is followed by an object in Dativ) DEN FreundeN.
"Des" is the article for Genetiv, masculine and neuter. Example for masculine: the apple of the man - der Apfel DES ManneS; neuter: the toy of the kid - das Spielzeug DES KindES