This is a box with a border around it. Note which side of the box is red.

Try editing the selected example, or select a different example:

border-top-color: red;
border-top-color: rgb(255, 128, 0);
border-top-color: hsla(240, 50%, 25%, 0.75);
border-top-color: #ffbb00;
border-top-color: currentColor;
border-top-color: transparent;