I did some digging and found where it can be fixed. The page MediaWiki:Css/base.css - The Official Terraria Wiki
needs to be updated, specifically the custom notice boxes and borders for green, red, and yellow. Whoever does it could use Colors HSL
to pick some colors values. I think hsl (117, 74%, 34%) would look better for the green box and hsl (117, 74%, 10%) would look better for the green borders.
Unfortunately, I can't change it; a mod needs too. But if one sees this, it should be a very quick fix!