CSS border-color Property
The css border-color property sets the color of an element’s four borders. This property can have from one to four values, made up of the elementary properties:border-top-color, border-right-color, border-bottom-color, border-left-color. The default color is the currentColor of each of these values. If you provide one value, it sets the color for the element. Two values set the horizontal and vertical values, respectively. Providing three values sets the top, vertical, and bottom values, in that order. Four values set all for sides: top, right, bottom, and left, in that order.