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 changed when the original Gen I and II games were ported to Virtual Console, which included HQ digital uploads of artwork of some of the older Pokémon.
Source: https://kotaku.com/pokemon-ken-sugimori-original-art-red-blue-gold-silver-1850352781