<!DOCTYPE html>
<html>
<style>
    .box {
        height: 50px;
        display: inline-block;
        zoom: 2;
    }
    .green-box {
        width: 100px;
    }
    .repeat-box {
        width: 400px;
    }
    .green-background {
        background-color: green;
    }
    .rgb-background {
        background: linear-gradient(
            to right,
            red,
            red 12.5%,
            green 12.5%,
            green 37.5%,
            blue 37.5%,
            blue 50%,
            red 50%,
            red 62.5%,
            green 62.5%,
            green 87.5%,
            blue 87.5%
        );
    }
</style>
<body>
    <div class="box green-box green-background"></div>
    <br>
    <div class="box repeat-box rgb-background"></div>
</body>
</html>