multi-account-containers/data/chrome.css

/* containers experiment */
.tabbrowser-tab[usercontextid] {
  background-image: linear-gradient(to right, var(--identity-tab-color) 0%, var(--identity-tab-color) 100%) !important;
  background-size: var(--identity-stroke-background-size) !important;
  background-repeat: no-repeat !important;
  background-position: 0 29px !important;
  --identity-stroke-background-size: auto 2px;
}

/* set defaults for ids as currently we don't set identity color */
[usercontextid="1"],
[data-identity-color="blue"] {
  --identity-tab-color: #37adff;
  --identity-icon-color: #37adff;
}

[data-identity-color="turquoise"] {
  --identity-tab-color: #00c79a;
  --identity-icon-color: #00c79a;
}

[usercontextid="3"],
[data-identity-color="green"] {
  --identity-tab-color: #51cd00;
  --identity-icon-color:  #51cd00;
}

[data-identity-color="yellow"] {
  --identity-tab-color: #ffcb00;
  --identity-icon-color: #ffcb00;
}

[usercontextid="2"],
[data-identity-color="orange"] {
  --identity-tab-color: #ff9f00;
  --identity-icon-color: #ff9f00;
}

[data-identity-color="red"] {
  --identity-tab-color: #ff613d;
  --identity-icon-color: #ff613d;
}

[usercontextid="4"],
[data-identity-color="pink"] {
  --identity-tab-color: #ff4bda;
  --identity-icon-color: #ff4bda;
}

[data-identity-color="purple"] {
  --identity-tab-color: #af51f5;
  --identity-icon-color: #af51f5;
}

.tabbrowser-tab[usercontextid] .tab-background-start:not([selected="true"]) {
  background-image: linear-gradient(to left, var(--identity-tab-color) 0%, var(--identity-tab-color) 50%, transparent 50%, transparent 100%);
  background-position: 0 28px;
  background-size: var(--identity-stroke-background-size);
  background-repeat: no-repeat;
}

.tabbrowser-tab[usercontextid][afterhovered=true] .tab-background-start:not([selected="true"]) {
  background-image: linear-gradient(to left, var(--identity-tab-color) 0%, var(--identity-tab-color) 22%, transparent 30%, transparent 100%);
}

.tabbrowser-tab[usercontextid]:hover .tab-background-start:not([selected="true"]) {
  background-image: linear-gradient(to left, var(--identity-tab-color) 0%, var(--identity-tab-color) 70%, transparent 80%, transparent 100%);
}

.tabbrowser-tab[usercontextid] .tab-background-start[selected="true"]::before {
  background-image: linear-gradient(to left, var(--identity-tab-color) 0%, var(--identity-tab-color) 30%, transparent 100%),
                    url(chrome://browser/skin/tabbrowser/tab-selected-start.svg) !important;
  background-size: var(--identity-stroke-background-size), 100% 100% !important;
  background-position: 0px 28px, 0;
  background-repeat: no-repeat;
}

.tabbrowser-tab[usercontextid] .tab-background-end:not([selected="true"]) {
  background-image: linear-gradient(to right, var(--identity-tab-color) 0%, var(--identity-tab-color) 50%, transparent 50%, transparent 100%);
  background-position: 0 28px;
  background-size: var(--identity-stroke-background-size);
  background-repeat: no-repeat;
}

.tabbrowser-tab[usercontextid][beforehovered=true] .tab-background-end:not([selected="true"]) {
  background-image: linear-gradient(to right, var(--identity-tab-color) 0%, var(--identity-tab-color) 22%, transparent 30%, transparent 100%);
}

.tabbrowser-tab[usercontextid]:hover .tab-background-end:not([selected="true"]) {
  background-image: linear-gradient(to right, var(--identity-tab-color) 0%, var(--identity-tab-color) 70%, transparent 80%, transparent 100%);
}

.tabbrowser-tab[usercontextid] .tab-background-end[selected="true"]::before {
  background-image: linear-gradient(to right, var(--identity-tab-color) 0%, var(--identity-tab-color) 30%, transparent 100%),
                    url(chrome://browser/skin/tabbrowser/tab-selected-end.svg) !important;
  background-size: var(--identity-stroke-background-size), 100% 100% !important;
  background-position: 0 28px, 0;
  background-repeat: no-repeat;
}

.tabbrowser-tab[usercontextid] .tab-background-middle {
  background-position: 0 28px, 0;
  background-repeat: repeat-x;
  background-size: var(--identity-stroke-background-size), auto;
  background-image: linear-gradient(to right, var(--identity-tab-color) 0%, var(--identity-tab-color) 100%), none;
}

.tabbrowser-tab[usercontextid] .tab-background-middle[selected="true"] {
  background-image: url(chrome://browser/skin/tabbrowser/tab-active-middle.png),
                    linear-gradient(to right, var(--identity-tab-color) 0%, var(--identity-tab-color) 100%),
                    none;
  background-position: 0, 0 28px, 0;
  background-size: var(--tab-stroke-background-size), var(--identity-stroke-background-size), auto;
  background-repeat: repeat-x;
}
/* end containers experiment */

.tabs-newtab-button .toolbarbutton-icon[type="menu"] {
  margin-inline-end: 0;
}

.tabs-newtab-button .toolbarbutton-menu-dropmarker {
  display: none;
}

.new-tab-overlay {
  visibility: visible;
  block-size: 200px;
  inline-size: auto;
  display: block;
  background: transparent;
  position: absolute;
  -moz-appearance: none;
  offset-block-start: 29px;
}
.new-tab-overlay[hidden=true] {
  display: none;
}

.new-tab-overlay menuitem {
  background: white;
  margin-block-end: 12px;
  border-radius: 20px;
  -moz-appearance: none;
  color: #4b4b4b;
  padding: 6px;
  font-size: 1.2rem;
  box-shadow: 3px 7px 7px #0006;
  --icon-size: 26px;
  /* Limited width to 8chars roughly */
  inline-size: calc(calc(8*0.68em) + var(--icon-size) + 3px);
}

.new-tab-overlay .menuitem-iconic[data-usercontextid] > .menu-iconic-left > .menu-iconic-icon {
  block-height: var(--icon-size);
  block-width: var(--icon-size);
}

.menuitem-iconic[data-usercontextid] > .menu-iconic-left {
  visibility: visible;
}