Template:Navigation/styles.css

body {
  --tg-color-surface-2: #f5f5f7; /* Light */
}

@media (prefers-color-scheme: dark) {
  body {
    --tg-color-surface-2: #1e1e20; /* Dark */
  }
}

.template-navpill {
  background-color: var(--tg-color-surface-2) !important;
}