This is how I do it.
/*
Set accent color in dark mode.
*/
.theme-dark {
/*#F90 gold*/
--accent-h: 48!important;
--accent-s: 100%!important;
--accent-l: 50%!important;
}
/* Set dark text on buttons and menu highlights for better contrast.
Settings sidebar highlight doesn't work yet. */
.theme-dark button.mod-cta,
.theme-dark .vertical-tab-nav-item.is-active {
color: black;
}
I have also posted a feature request for separate light and dark mode accent color settings. If you’d like to show support for it you can comment on it or press its heart button.