Menu bar background color not following themes

[TheNonexistent]

Description

The top menu bar does not follow the color scheme of the selected theme, the css variable --color-nav-bg is always provided by index.css and overrides any changes the theme makes.

Even when manually setting the --color-nav-bg variable inside the theme-<>.css, the variable is stripped from the final file served to the browser.

The default dark theme(arc-green) works as expected as it provides a --color-nav-bg variable.

Screenshots

Gitea Version

1.20.0 on docker

Can you reproduce the bug on the Gitea demo site?

No

Operating System

Debian Linux (Firefox and Chrome browsers)

Browser Version

Firefox 115.0.2

[denyskon]

Some variables need to be updated in your theme to work, check the changes to arc-green in #25111 (review)