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.
This guide explains everything about Xerneas and Yveltal to clear any dilemma.
Source: https://gamerant.com/pokemon-go-are-xerneas-and-yveltal-good-to-use/