Using outline:
.div1{
border: 3px solid black;
outline: 6px solid blue;
width: 100px;
height: 100px;
margin: 20px;
}
Using box-shadow:
.div2{
border: 5px solid green;
box-shadow: 0px 0px 0px 4px #000;
width: 100px;
height: 100px;
margin: 20px;
}
Using a pseudo element:
.div3 {
position: relative;
border: 5px solid #000;
width: 100px;
height: 100px;
margin: 20px;
}
.div3:before {
content: " ";
position: absolute;
border: 5px solid blue;
z-index: -1;
top: 5px;
left: 5px;
right: 5px;
bottom: 5px;
}
http://jsfiddle.net/MadalinaTn/bvqpcohm/2/