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.
You can also unhide any photos that have been previously hidden by selecting them and tapping Unhide from the same menu.
Source: https://www.devicemag.com/how-to-lock-photos-on-iphone/