blockquote {
background-color: green;
position: relative;
color: white;
padding: 15px 25px;
margin: 10px 10px 0;
}
blockquote:after {
border: 15px solid;
border-color: green transparent transparent;
top: 100%; left: 10px;
width: 0; height: 0;
position: absolute;
content: '';
}