Synonyms that are in the dictionary are marked in green. Synonyms that are not in the dictionary are marked in red.
Antonyms that are in the dictionary are marked in green. Antonyms that are not in the dictionary are marked in red.
As for the revamped Dark mode, the developers have changed the background colour to match the aesthetics of the dark theme and help reduce eye strain.
Dark mode can save battery life and by making the background of your phone darker.