Thanks for the link, I’m not sure my problem fits into that category.
https://paste.pics/0392994b75f34012cd0df56847e8fdf6
You can find an image of the problem I’m finding. I understand WordPress doesn’t know CSS code, but normally it highlights recognised variables?
Thanks so much George! Massively appreciated. Seems like you’ve nailed the issue. I’ve looked in a couple of spots on our WordPress backend, including “additional CSS” sections of the page builders… but can’t find the offending code. Do you know if this is something that I can access through Astra Pro or regular Gutenberg builder, or will it require getting under-the-hood? I’ve not tried that before and am slightly concerned of making a terrible error!