.header {
  background: #fff;
}

@media (prefers-color-scheme: dark) {
  .header {
    background: #232425;
  }
}

@media (prefers-color-scheme: light) {
  .header {
    background: #fff;
  }
}

[data-theme=dark] .header {
  background: #232425;
}

[data-theme=light] .header {
  background: #fff;
}