yea checked on light mode and that worked but really they should have designed this to work on both with a static colour rather than dynamic based on light/dark mode hence bad UX rather than bad UI
That's the thing - they probably did design this to be a static colour - only your email client has piped up and decided you don't want that dark text being displayed on a dark background, so overridden it and made it light.
There are a few ways to to try and work around it, sadly the most reliable is to convert to an image, which brings a whole load of accessibility and potentially privacy concerns - pretty much everything else is a war between the people creating emails and the people creating email clients, with the battle lines drawn by users complaining that the wrong colour was displayed in the wrong context. While there is now CSS functionality for detecting dark mode, this is often stripped / ignored / unsupported by the renderers used in email clients, so even the thing designed to prevent the issue is useless in an email context.