I guess you are referring to Dark mode?
Paste the following in CSS Snippets
/* Theme colors */
.theme-light.minimal-light-contrast .workspace-fake-target-overlay.is-in-sidebar,
.theme-light.minimal-light-contrast .titlebar,
.theme-light.minimal-light-contrast .workspace-ribbon.mod-left:not(.is-collapsed),
.theme-light.minimal-light-contrast .mod-left-split,
.theme-light.minimal-light-contrast.minimal-status-off .status-bar,
.theme-light.minimal-light-contrast.is-mobile .workspace-drawer.mod-left,
.excalidraw.theme--dark,
.theme-dark {
--text-faint:hsl(var(--base-h),var(--base-s),calc(var(--base-d) + 35%));
--icon-muted:0.6;
}
35% works for me, and 0.6 for icon-mute works for me. Change the number according to your own preference.