function colour_change(flash_hex) {
  var colour_class = {'0xF4282B': 'red',
                      '0x66CC00': 'green',
                      '0xFF6600': 'orange',
                      '0x00CCFF': 'blue'
                     };
  var footer_nav = document.getElementById('footer_nav');
  if (footer_nav) footer_nav.className = colour_class[flash_hex];
}