I remember tokaku's tip about this:
Screenshot the gamplay (which you already did)
paste it into scorebar-colour.png in the photo editor (remember to paste it in another layer)
Lower down the opacity/transparency to around 50%, then scale (remember to hold shift while doing so) and move until the HP bar in the screenshot overlaps perfectly with the element.
Move that element in line to the background and save it (also remember to not left the screenshot layer visible before doing so).