The bulb is a #73, It is called a wedge bulb. You can take off the clear plastic top part of button by placing a razor blade between side of clear button and the black outer edge a carefully pry up and when it starts to lift move to the other side of button so it comes up even. You will see the small bulb, gently push down to tighten. This works with the large buttons also, they use a # 159 wedge bulb. Or open main door and while machine is turned off pull down on the white actuator you will see the bulb. replace the actuator by pushing back into place, you will hear a click.
Hope this helps, Good luck!