Default revealjs link colour fails text contrast at normal sizes

[cwickham]

I have:

• searched the issue tracker for similar issues
• installed the latest version of Quarto CLI
• formatted my issue following the Markdown guide

Bug description

The default revealjs theme sets $link-color to #2a76dd. On the default #fff background, the contrast is 4.44:1. WCAG 2.2 SC 1.4.3 Contrast (Minimum) requires 4.5:1 for text that is not large.

Slide body text is 40px, so body links pass (large text needs 3:1). Links in smaller text fail, for example in the footer (18px, and 14px on a 320px viewport), in .smaller slides, and in captions.

The colour comes from quarto.scss L40-L41. axe reports this on the quarto.org revealjs demo footer.

Steps to reproduce

---
format: revealjs
footer: "[quarto.org](https://quarto.org)"
---

## Slide

See [the Quarto website](https://quarto.org).

1. Render the file.
2. Measure the footer link colour against the slide background.

Actual behavior

The footer link is #2a76dd on #fff, at 4.44:1.

Expected behavior

The default link colour gives at least 4.5:1 on the default background.

AI helped investigate this issue. The investigation used a local clone of quarto-cli (see "Using AI tools to investigate" in CONTRIBUTING.md).

Your environment

• IDE: Positron 1.134.0
• OS: macOS 26.6.2 (build 25G83)

Quarto check output

Quarto 1.11.4

[✓] Checking environment information...
      Quarto cache location: /Users/charlottewickham/Library/Caches/quarto

[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.10.0: OK
      Dart Sass version 1.101.0: OK
      Deno version 2.7.14: OK
      Typst version 0.15.1: OK

[✓] Checking versions of quarto dependencies......OK

[✓] Checking Quarto installation......OK
      Version: 1.11.4
      Path: /Applications/quarto/bin


[✓] Checking tools....................OK
      TinyTeX: v2026.04
      Chrome Headless Shell: 150.0.7871.115
      VeraPDF: 1.28.2


[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/charlottewickham/Library/TinyTeX/bin/universal-darwin
      Version: 2026


[✓] Checking Chrome Headless....................OK
      Using: Chrome Headless Shell installed by Quarto
      Path: /Users/charlottewickham/Library/Application Support/quarto/chrome-headless-shell/chrome-headless-shell-mac-arm64/chrome-headless-shell
      Version: 150.0.7871.115


[✓] Checking basic markdown render....OK


[✓] Checking R installation...........OK
      Version: 4.6.0
      Path: /Library/Frameworks/R.framework/Versions/4.6/Resources
      LibPaths:
        - /Users/charlottewickham/Library/R/arm64/4.6/library
        - /Library/Frameworks/R.framework/Versions/4.6/Resources/library
      knitr: 1.51
      rmarkdown: 2.31


[✓] Checking Knitr engine render......OK


[✓] Checking Python 3 installation....OK
      Version: 3.12.2
      Path: /Users/charlottewickham/.pyenv/versions/3.12.2/bin/python3
      Jupyter: 5.9.1
      Kernels: python3


[✓] Checking Jupyter engine render....OK


[✓] Checking Julia installation...