.border {

    width: 0;

    height: 0;

    border-style:solid;

    border-width: 0 50px 50px;

    border-color: transparent transparent #d9534f;

    position: relative;

}

​

.border:after{

    content: '';

    border-style:solid;

    border-width: 0 40px 40px;

    border-color: transparent transparent #96ceb4;

    position: absolute;

    top: 0;

    left: 0;

}