Theres no secret when it comes to make a simple circumferences just using css, it's as simple as creating a circle with a border , although making quarters , halfs and three quarters circumferences is not much harder!
.circonf {
width: 50px;
height: 50px;
border-radius: 50%;
border: 10px solid #3498db;
box-sizing: border-box;
border-top-color: lighten(#3498db, 20%);
border-left-color: lighten(#3498db, 10%);
border-right-color: lighten(#3498db, 30%);
}
As you can see on the example above the code is not that complex, and you don't even need to use any pseudo-element , they key is setting the border as you normally do and give it a transparent color, or any other color really, and give diferent colors to the top, right, bottom & left.
Also as an extra tip you can set the border to grow inwards or outwards by setting the box-sizing .
Hope your learned something usefull, happy codding!