I can\'t seem to see any results on google unless I use jQuery and I\'m not so sure if jQuery and javascript plain work together.
Try using data-* attribute to store color replacement, original background color of button element or initial setting; JSON.parse() , JSON.stringify() , Array.prototype.reverse() to toggle data-* attribute values that set background of input type="button" element; onclick event.
Not certain if requirement is to toggle background color, or reset to original color once ?