This is not an answer to the original question, but does not quite fit into a comment, and yet it is an extremely useful and fully customizable tool to solve the hard-to-see issue immediately.
If you use GreaseMonkey and know CSS, you can easily fix such issues with any site you use. Just create a new userscript as follows:
// ==UserScript==
// @name Display Control
// @namespace user21820
// @match *://stackoverflow.com/*
// @match *://meta.stackoverflow.com/*
// @match *://superuser.com/*
// @match *://meta.superuser.com/*
// @match *://serverfault.com/*
// @match *://meta.serverfault.com/*
// @match *://askubuntu.com/*
// @match *://meta.askubuntu.com/*
// @match *://*.stackexchange.com/*
// @match *://stackapps.com/*
// @match *://mathoverflow.net/*
// @version 1
// @grant none
// ==/UserScript==
style=document.createElement('style');
document.head.appendChild(style);
stylesheet=style.sheet;
function css(selector,property,value)
{
try{ stylesheet.insertRule(selector+' {'+property+':'+value+'}',stylesheet.cssRules.length); }
catch(err){}
}
css(".post-text blockquote","background","#ddd !important");
css(".post-text blockquote","border-left","2px solid #bbb !important");
To figure out what CSS rules to construct (for other issues on other websites), you would need to learn how to inspect the DOM content (which may be easy or hard depending on your browser).