Rated 5 out of 5 stars

FF57+, not quite like i used to know it but close.
preview: https://imgur.com/LZO7EtU

userChrome.css:


:root:-moz-lwtheme {

/*no stripes in main bar*/
--toolbar-bgcolor: rgba(255,255,255,0) !important;
/*active tab green bar*/
--tab-line-color: rgb(0,190,15) !important;

}

/* active tab - green font and icons*/
.tabbrowser-tab[selected=true] {
color: rgb(0,190,15)!important;

}
/*inactive tab */
.tabbrowser-tab {
background-color: #9c9c9c33!important;
}