styles/xf.theme.dark.less (7 lines of code) (raw):

/* Overrides specific for Dark theme ===================================== */ .xf-theme-dark { } .xf-header { .border-box; border: 1px solid #212325; .box-shadow(~"inset 0 1px 0 rgba(255,255,255,.2), 0 1px 1px rgba(0,0,0,.55)"); }