Internally we use css variable with id, so its doable, but a bit tricky to obtain these id at the moment.
Two hacks to get these ids:
- Open any formula, and bind this to your colors. Switch to js, and the id will be display. Then you can use var(–YOUR_ID) on your css style.
- Open the devtool on your editor, and search for the html element (the one from the iframe if you are in the editor). You will see a bunch of css variable defined here, including your colors.
Hope this help !