background doesn't work as a color in revealjs unless it's explicitly set

[cscheid]

repro:

---
title: Hello, `_brand.yml`!
brand:
  typography: 
    monospace:
      family: Inconsolata
      size: 1em
      color: foreground
      background-color: background
    base:
      family: Open Sans
    headings:
      family: Montserrat
    fonts:
      - family: Inconsolata
        source: google
      - family: Open Sans
        source: google
      - family: Montserrat
        source: google
---

## Links

Download the Positron Beta here: <https://positron.posit.co/download.html>

Docs for `_brand.yml`: <https://posit-dev.github.io/brand-yml/>, <https://quarto.org/docs/authoring/brand.html>

## Placeholder text

This is an example document with a [number](https://quarto.org) of `features` to help you come with a nicely branded document.

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quarto render --to html works, quarto render --to revealjs doesn.t

[cderv]

FWIW I can handle revealjs issue, even if they are brand related.