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.
Not only the colors more pronounced (and in some cases, entirely different, such in the case of Ivysaur), you can also see the watercolors bleed over the lines of the artwork, giving the art a much more handmade quality.
Source: https://comicbook.com/gaming/news/pokemon-ken-sugimori-original-artwork-red-blue/