button.css

/* Buttons */

.action {
    -premailer-cellpadding: 0;
    -premailer-cellspacing: 0;
    -premailer-width: 100%;
    margin: 30px auto;
    padding: 0;
    text-align: center;
    width: 100%;
}

.button {
    -webkit-text-size-adjust: none;
    border-radius: 4px;
    color: #fff;
    display: inline-block;
    overflow: hidden;
    text-decoration: none;
}

.button-blue,
.button-primary {
    background-color: #2d3748;
    border-bottom: 8px solid #2d3748;
    border-left: 18px solid #2d3748;
    border-right: 18px solid #2d3748;
    border-top: 8px solid #2d3748;
}

.button-green,
.button-success {
    background-color: #48bb78;
    border-bottom: 8px solid #48bb78;
    border-left: 18px solid #48bb78;
    border-right: 18px solid #48bb78;
    border-top: 8px solid #48bb78;
}

.button-red,
.button-error {
    background-color: #e53e3e;
    border-bottom: 8px solid #e53e3e;
    border-left: 18px solid #e53e3e;
    border-right: 18px solid #e53e3e;
    border-top: 8px solid #e53e3e;
}