Module:Infobox/styles-test.css

/* Base styles */
.infobox {
  background-color: #f8f9fa;
  color: black;
  border: 1px solid #a2a9b1;
}

/* System dark mode */
@media (prefers-color-scheme: dark) {
  .infobox {
    background-color: #1e1e1e;
    color: #f0f0f0;
    border-color: #444;
  }
}

/* MediaWiki Vector 2022 dark skin override */
html[data-mw-theme="dark"] .infobox {
  background-color: #1e1e1e;
  color: #f0f0f0;
  border-color: #444;
}