userChrome.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
/* set default namespace to XUL */

.panel-subview-body {
  background-color: #131C29;
}

.subviewbutton {
  color: #ffffff;
}

.toolbaritem-combined-buttons {
  color: #efefef;
}

.customization-target, #TabsToolbar, #navigator-toolbox {
  background-color: #141415 !important;
}

#urlbar:-moz-lwtheme, #navigator-toolbox .searchbar-textbox:-moz-lwtheme {
  background: linear-gradient(270deg, #141415, #313640);
  animation: gradient 10s ease infinite;
  background-size: 400% 400%;
}

#urlbar:not([focused="true"]):-moz-lwtheme, #navigator-toolbox .searchbar-textbox:not([focused="true"]):-moz-lwtheme {
  border: 3px solid #00A0FF99 !important;
}

@keyframes gradient {
  0% {
    background-position: 0% 50%
  }
  50% {
    background-position: 100% 50%
  }
  100% {
    background-position: 0% 50%
  }
}

.panel-viewcontainer {
  color: #ffffff;
}

.tab-content {
  border: 2px solid #008FE5;
  border-style: none solid none none;
}

.tab-stack {
  background-color: #151A21;
}

.tab-stack:hover {
  background-color: #000000;
}

.titlebar-placeholder[type="pre-tabs"] {
  border-inline-end: none;
}

.toolbarbutton-animatable-box[brighttext], toolbar[brighttext] .toolbarbutton-animatable-box, toolbar[brighttext] .toolbarbutton-1 {
  fill: #01efff !important;
}

#navigator-toolbox>toolbar:not(#TabsToolbar):not(#toolbar-menubar), .browserContainer>findbar, #browser-bottombox {
  background-color: #141415 !important;
}

.downloadsPanelFooterButton,richlistitem[type="download"]{
  color:#000000 !important;
}