"No apples are blue."
Translation:Żadne jabłka nie są niebieskie.
Here's a joke about an English lecturer who is teaching grammar to his students. Lecturer: 'In English, there is no such thing as a double negative, since two negatives always make a positive. Of course, it goes without saying that there's also no case of two positives making a negative.' Disinterested student, rolling their eyes: 'Yeah, right!'
Completely, I'm afraid.
Firstly, "niebieski" is masculine singular, while apples are plural (not masculine-personal plural), for which the right form is "niebieskie".
Secondly, the sentence is supposed to say that apples "aren't blue" (you should negate 'being blue'), while you negated "apples". Your sentence aims to say "It's not the apples that are blue (something else is blue)".
And finally, you didn't use the word "żadne" which is required in the translation of such an English sentence.
I think the English form closest would be "no, apples aren't blue". In English this sounds as if you have explained something before and the listener does not believe you so your final attempt to convince them is "No apples aren't blue". No, pigs don't fly". These two negatives produce a strong negative statement.