Sounds like a Tolkien book to me.

There's a wonderful game I played called crosscode, and one of the areas is called "Vermillion Wastelands" and everything is red. Also that's the first time I heard the word so can't relate

Vert means green in french (the t is silent)

I think you're having a Mengele Effect about the Mandela Effect

Verdant, verde, vermilion.

Chameleons are green. Verde is green. Vermillion is green 100%

Chartreuse as well tbh, just the other way around.

I would be happy for it to switch places with Chartreuse, which feels strongly like a red word and is definitely not a bright yellow-green

I'm finding this out now from this post.

When people named flowers as 'Vermillion' I assumed the stems and leaves were some weird shade that I wasn't recognizing.

I played too much "Sword of Vermilion" on Sega Genesis to have this particular issue.