This userstyle modifies Firefox's Identity-Box.
It is a modified version of a css found at userstyles.org several years ago and unsuccessfully searched for.

/* START ----------------------------------------------------------------------

@namespace xul url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
@-moz-document url("chrome://browser/content/browser.xul") {

#urlbar-throbber, #identity-icon-label, #identity-icon-country-label {visibility: collapse !important;}
#page-proxy-favicon {-moz-image-region: rect(0, 16px, 16px, 0) !important; opacity: 1 !important; margin-left: 2px !important; margin-right: 3px !important;}

#identity-box {background-image: -moz-linear-gradient(#EEEEFF,#DDDDFF) !important; margin-right: 4px !important;}

#identity-box:not([open]):hover {box-shadow: 0 0 0 1px rgba(255,255,255,.6) inset !important;}
#identity-box[open] {box-shadow: 0 1px 0 rgba(0,0,0,.05) inset, 0 0 2px rgba(0,0,0,.2) inset !important;}
#identity-box:hover #page-proxy-favicon {opacity: .8 !important;}
#identity-box:not([open]):hover {background-image: -moz-linear-gradient(#F5F7FD,#F0F3FD,#ECF0FC) !important;}
#identity-box[open] {background-image: -moz-linear-gradient(#CDD1DE,#D8DCE9,#E2E6F3) !important;}

#identity-box.verifiedIdentity {background-image: -moz-linear-gradient(#D2F6BF,#6DBC5C,#79C349) !important;}
#identity-box.verifiedIdentity:not([open]):hover {background-image: -moz-linear-gradient(#CFF294,#76D162,#85DA54) !important;}
#identity-box.verifiedIdentity[open] {background-image: -moz-linear-gradient(#78B542,#59A949,#93DE64) !important;}

#identity-box.verifiedDomain {background-image: -moz-linear-gradient(#FBEE7B,#E8CA45,#F2E785) !important;}
#identity-box.verifiedDomain:not([open]):hover {background-image: -moz-linear-gradient(#FFFCC7,#F1DC70,#F2E88E) !important;}
#identity-box.verifiedDomain[open] {background-image: -moz-linear-gradient(#D1B84C,#D7AD36,#FEF5A2) !important;}

#identity-box.mixedContent {background-image: -moz-linear-gradient(#FFE2DF,#F5C8C1,#FFD6D2) !important;}
#identity-box.mixedContent:not([open]):hover {background-image: -moz-linear-gradient(#FFF7F6,#FFD6D2) !important;}
#identity-box.mixedContent[open] {background-image: -moz-linear-gradient(#C8ABA8,#FFD6D2) !important;}

#identity-icon-labels {visibility: visible !important;}

#urlbar:-moz-any([pageproxystate="invalid"],[focused]) #identity-icon-labels,
#main-window[stylish-url^="https://"] #urlbar:not([level]) #identity-icon-labels {visibility: collapse !important;}

#identity-box #identity-icon-labels:after {display: -moz-box !important; -moz-box-align: center !important;
color: rgba(0,0,0,.76) !important; text-shadow: none !important; margin-left: -2px !important;}

#identity-box #identity-icon-labels:after {content: "" !important;}
#identity-box.verifiedIdentity #identity-icon-labels:after {content: "TRUSTED" !important; margin-right: 2px !important;}
#identity-box.verifiedDomain #identity-icon-labels:after {content: "SECURE" !important; margin-right: 2px !important;}
#identity-box.mixedContent #identity-icon-labels:after {content: "MIXED" !important;  margin-right: 2px !important;}

/* Smart Location */
#urlbar:not([focused]) :-moz-any(stsegment.protocol, stsegment.querry, stsegment.index) {visibility: collapse !important;}
#main-window[stylish-url^="https://"] #urlbar:not([level]) stsegment.protocol {visibility: visible !important;}
stsegment[class="subdomain www"] {display: block !important;}

}

/* END ------------------------------------------------------------------------