I’ll note that you can use :after
and :before
to fake extra borders (as long as you don’t need more than two additional colors).
For example:
.hi {
width: 50px;
height: 50px;
position: relative;
border: 10px solid green;
}
.hi:after {
content: '';
border-right: 10px solid blue;
position: absolute; top: -10px; left: -10px; right: -10px; bottom: -10px;
}
.hi:before {
content: '';
border-top: 10px solid red;
position: absolute; top: -10px; left: -10px; right: -10px; bottom: -10px;
}
yields: