Maybe much like Robin Rendle, author of this CSS-tricks article, I had heard a lot about Design Tokens, but while I initially thought of them more or less like conceptual tokens, a clearly defined terminilogy (e.g. primary-color and not color1 or success-color). This article explained to me what it should (or could) be: a tech-stack agnostic file (in most orgs this would probably be a json format) that contains all the design-variables / tokens, which is referenced in all other build steps as a single source of truth.
While I think this is great in theory, and might be easy to set up if you’re starting from scratch, maybe good old communication may work just as well. Especially if you have multiple single sources of truth per tech stack (e.g. a single source of truth in your design package, your CSS-build package and your mobile development package).