Firefox 149.0beta9 Schriftfarbe der Tab im Split-View-Modus ändern

/* Icon "Add Split View" and "Separate Split View" in Tab context menu */
#context_moveTabToSplitView, #context_separateSplitView {
    background-image: url("chrome://browser/skin/split-view-left-16.svg") !important;
    fill: red !important;
    padding-inline-start: calc(1em + 4px) !important;
    background-position: left 1em center;
    background-repeat: no-repeat;
    background-size: 16px;
}