JSFiddle - React, Tailwind, and code Playground

CSS

a { color: #FF0001; }
a:visited { color: #FF0000; }

JavaScript

var url_array = new Array('http://root.cz', 'http://lupa.cz', 'http://zdrojak.root.cz', 'http://seznam.cz', 'http://user.centrum.cz');
var visited_array = new Array();

var link_el = document.createElement('a');
var computed_style = document.defaultView.getComputedStyle(link_el, "");

for (var i = 0; i < url_array.length; i++) {
    link_el.href = url_array[i];
    if (computed_style.getPropertyValue("color") == 'rgb(255, 0, 0)') {
        visited_array.push(url_array[i]);
    }
}

alert(visited_array);