meter {
    /* Reset the default appearance */
  /* -webkit-appearance: none; */
     -moz-appearance: none;
          /* appearance: none; */
            
  width: 100%;
  height: .8em;
    
    /* Applicable only to Firefox */
  background: none;
  /* background-color: rgba(0,0,0,0.1); */
}

meter::-webkit-meter-bar {
  background: none;
  background-color: rgba(0,0,0,0.1);
}

meter[value="1"]::-webkit-meter-optimum-value { background: red; }
meter[value="2"]::-webkit-meter-optimum-value { background: yellow; }
meter[value="3"]::-webkit-meter-optimum-value { background: orange; }
meter[value="4"]::-webkit-meter-optimum-value { background: green; }

meter[value="1"]::-moz-meter-bar { background: red; }
meter[value="2"]::-moz-meter-bar { background: yellow; }
meter[value="3"]::-moz-meter-bar { background: orange; }
meter[value="4"]::-moz-meter-bar { background: green; }