meter {
    /* Reset the default appearance */
    margin: 0 auto 1em;
    width: 100%;
    height: .5em;

    /* 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;
}