hetzner-custom.css

#pageHeader,
#topMenu > .layoutFluid,
#main,
#pageFooter {
  max-width: 1400px;
  margin: auto;
}
.quoteBoxAuthor {
  font-size: 12px;
}
.quoteBoxAuthor > .quoteAuthorAvatar .userAvatarImage {
  height: 48px !important;
  width: 48px !important;
}
.quoteBoxAuthor > .quoteAuthorAvatar + .quoteBox {
  margin-left: 70px;
}
.quoteBoxAuthor > .quoteAuthorAvatar::before {
  left: 55px;
}
.quoteBoxAuthor > .quoteAuthorAvatar::after {
  left: 56px;
}
.boxHeadline > h1 a, 
.boxSubHeadline > h2 a,
.messageHeadline > h1 {
  color: #333 !important;
}
.messageBody {
  color: #333;
  font-size: 14px;
}
.messageSignature {
  font-size: 10px;
}
.messageSidebar .userAvatarImage {
  width: 100px !important;
  height: 100px !important;
}
.adminMessage {
  background-color: #dae5f0;
}
.adminMessage .messageContent {
  background-color: #edf2f7 !important;
}

hetzner-custom.user.js

// ==UserScript==
// @name        Hetzner Forum User Style
// @namespace   hetzner
// @description Applies custom user styles to the Hetzner forum
// @include     http://forum.hetzner.de/*
// @include     https://forum.hetzner.de/*
// @updateURL   https://gist.github.com/driehle/aeb3e81efb03d35130d1/raw/hetzner-custom.user.js
// @require     https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js
// @version     5
// @grant       none
// @run-at      document-start
// ==/UserScript==

var $ = window.jQuery;

var style = $("<link />");
style.attr('rel', 'stylesheet');
style.attr('type', 'text/css');
style.attr('href', 'https://rawgit.com/driehle/aeb3e81efb03d35130d1/raw/hetzner-custom.css');
$("head").append(style);
  
$(document).ready(function() {
  $(".userTitleBadge.blue").parents("article").addClass("adminMessage");
})