Even though GitHub Readme files (typically ./readme.md) are Markdown, and although Markdown supports HTML, you can’t put <style> or <script> tags init. (Well, you can, they just get stripped.) So you can’t apply custom styles there. Or can you?

  1. You can use SVG as an <img src="./file.svg" alt="" /> (anywhere).
  2. When used that way, even stuff like animations within them play (wow).
  3. SVG has stuff like <text> for textual content, but also <foreignObject> for regular ol’ HTML content.
  4. SVG support <style> tags.
  5. Your readme.md file does support <img> with SVG sources.

Sindre Sorhus combined all that into an example.

That same SVG source will work here:

source