meter {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
  margin: 0 auto 1em;
  width: 100%;
  height: 0.5em;
  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;
}