:root {
--main-bg-color: coral;
}
@media (prefers-color-scheme: dark){
:root {
--main-bg-color: red;
}
}
.element{
background-color: var(--main-bg-color);
}
/* https://css-tricks.com/a-complete-guide-to-dark-mode-on-the-web */
@media (prefers-color-scheme: dark) {
img {
filter: brightness(.8) contrast(1.2);
}
}