code: function sortPageBackground(elmStack) {
  	let bodyIndex = elmStack.indexOf(document.body);
  	let bgNodes = elmStack;
  
  	if (
  		// Check that the body background is the page's background
  		bodyIndex > 1 && // only if there are negative z-index elements
  		!color.elementHasImage(document.documentElement) &&
  		color.getOwnBackgroundColor(
  			window.getComputedStyle(document.documentElement)
  		).alpha === 0
  	) {
  		// Remove body and html from it's current place
  		bgNodes.splice(bodyIndex, 1);
  		bgNodes.splice(elmStack.indexOf(document.documentElement), 1);
  
  		// Put the body background as the lowest element
  		bgNodes.push(document.body);
  	}
  	return bgNodes;
  }
docs: Look at document and body elements for relevant background information
  @method sortPageBackground
  @private
  @param {Array} elmStack
  @returns {Array}