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.
Open up your phone's settings, by swiping down twice from the top of the screen and tapping the gear-shaped icon in the panel that appears.
Source: https://www.computerworld.com/article/3684513/advanced-android-adjustments.html