Mneumonic device: Ciemny : Chimney. It is dark inside a chimney. Dark colors are inside.
According to the dictionary "czy" can mean one of three things
a yes/no question word
"if" in relative speech
or (some resources split this meaning into two)
in questions - you have a choice, but you have to choose, and can choose only one
in statements - it is one thing or other , but the speaker is not sure (and doesn't really care) which one.
czy is mostly for questions
albo is more often for statements.
In a question:
chcesz kawę albo herbatę? do you want (coffee or tea) (possibe answers no, yes cofee, yes tea)
chcesz kawę lub herbatę? do you want (coffee or tea) (possibe answers no, yes cofee, yes tea, yes both)
chcesz kawę czy herbatę? (which one) do you want coffee or tea? (possible answers coffee, tea)
Well, the Polish phrase repeats "kolor"... plus shouldn't it be "or a dark one" then?
While comparing two thindg ilike n this sentence we don`t repeat the word "colour", instead of it we say " Is it a bright colour or a dark one?"
Well, Duolingo uses the American English for main answers, as it's an American company. Well, unless the American answer is ambiguous (between the dialects) while the British is not (pants vs trousers, for example).