[google-chrome] Background color not showing in print preview

I used purgatory101's answer but had trouble keeping all colours (icons, backgrounds, text colours etc...), especially that CSS stylesheets cannot be used with libraries which dynamically change DOM element's colours. Therefore here is a script that changes element's styles (background-colour and colour) before printing and clears styles once printing is done. It is useful to avoid writing a lot of CSS in a @media print stylesheet as it works whatever the page structure.

There is a part of the script that is specially made to keep FontAwesome icons color (or any element that uses a :before selector to insert coloured content).

JSFiddle showing the script in action

Compatibility: works in Chrome, I did not test other browsers.

function setColors(selector) {
  var elements = $(selector);
  for (var i = 0; i < elements.length; i++) {
    var eltBackground = $(elements[i]).css('background-color');
    var eltColor = $(elements[i]).css('color');

    var elementStyle = elements[i].style;
    if (eltBackground) {
      elementStyle.oldBackgroundColor = {
        value: elementStyle.backgroundColor,
        importance: elementStyle.getPropertyPriority('background-color'),
      };
      elementStyle.setProperty('background-color', eltBackground, 'important');
    }
    if (eltColor) {
      elementStyle.oldColor = {
        value: elementStyle.color,
        importance: elementStyle.getPropertyPriority('color'),
      };
      elementStyle.setProperty('color', eltColor, 'important');
    }
  }
}

function resetColors(selector) {
  var elements = $(selector);
  for (var i = 0; i < elements.length; i++) {
    var elementStyle = elements[i].style;

    if (elementStyle.oldBackgroundColor) {
      elementStyle.setProperty('background-color', elementStyle.oldBackgroundColor.value, elementStyle.oldBackgroundColor.importance);
      delete elementStyle.oldBackgroundColor;
    } else {
      elementStyle.setProperty('background-color', '', '');
    }
    if (elementStyle.oldColor) {
      elementStyle.setProperty('color', elementStyle.oldColor.value, elementStyle.oldColor.importance);
      delete elementStyle.oldColor;
    } else {
      elementStyle.setProperty('color', '', '');
    }
  }
}

function setIconColors(icons) {
  var css = '';
  $(icons).each(function (k, elt) {
    var selector = $(elt)
      .parents()
      .map(function () { return this.tagName; })
      .get()
      .reverse()
      .concat([this.nodeName])
      .join('>');

    var id = $(elt).attr('id');
    if (id) {
      selector += '#' + id;
    }

    var classNames = $(elt).attr('class');
    if (classNames) {
      selector += '.' + $.trim(classNames).replace(/\s/gi, '.');
    }

    css += selector + ':before { color: ' + $(elt).css('color') + ' !important; }';
  });
  $('head').append('<style id="print-icons-style">' + css + '</style>');
}

function resetIconColors() {
  $('#print-icons-style').remove();
}

And then modify the window.print function to make it set the styles before printing and resetting them after.

window._originalPrint = window.print;
window.print = function() {
  setColors('body *');
  setIconColors('body .fa');
  window._originalPrint();
  setTimeout(function () {
    resetColors('body *');
    resetIconColors();
  }, 100);
}

The part that finds icons paths to create CSS for :before elements is a copy from this SO answer