Problem selbst gelöst mit folgenden Code:
CSS
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
#appmenu-button {
background: #A90101 !important;
}
#appmenu-button dropmarker:before {
content: "My Firefox" !important;
color: #FFFFFF !important;
text-shadow:none;
}
#appmenu-button .button-text {
display: none !important;
}
tabs.tabbrowser-tabs#tabbrowser#tabs{
background-color: transparent!important;
}
.tabbrowser-tab, .tabs-newtab-button {
background: transparent !important;
color: #ffffff !important;
text-shadow: 0px 0px 2px !important;
font-size: 0.9em !important;
border: #000000 1px solid !important;
padding-left: 4px !important;
padding-right: 4px !important;
box-shadow: inset 0px 0px 1em 0px rgba(255,255,255,.5) !important;
border-radius: 6px 6px 0px 0px !important;
height: 24px !important;
}
.tabbrowser-tab:not([pinned="true"]){
margin-left: 1px !important;
margin-right: 1px !important;
color: #ffffff !important;
}
.tabbrowser-tab[selected="true"]{
background: transparent !important;
color: #ffffff !important;
text-shadow: 0px 0px 2px !important;
box-shadow: inset 0px 0px 10px 0px #EE0000 !important;
}
/* privates Fenster/Tab */
#main-window[privatebrowsingmode=temporary] #appmenu-button {
background: #6913A3 !important;
}
#main-window[privatebrowsingmode=temporary]:not([disablechrome]) .tabbrowser-tab[selected=true]:not(:-moz-lwtheme) {
box-shadow: inset 0px 0px 10px 0px #8b00e9 !important;
}
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