CSS border-color property adds color to the element's border. For example,
h1 {
    border-style: solid;
    border-color: orange;
}
Browser Output
Here, the border-color property adds orange as a border color to the h1 element. 
CSS border-color Syntax
The syntax for the border-color property is as follows,
border-color: color | transparent;
Here,
color: specifies the color value in any formats such as color name,HEX,RGB, andHSLtransparent: sets the border color to be transparent
CSS border-color Example
Let's see an example of the border-color property,
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <link rel="stylesheet" href="style.css" />
        <title>CSS border-color</title>
    </head>
    <body>
        <p class="border-blue">border-color: blue;</p>
        <p class="border-green">border-color: rgb(0, 255, 0);</p>
        <p class="border-red">border-color: #ff0000;</p>
    </body>
</html>
p {
    /* sets the border style to solid */
    border-style: solid;
    padding: 8px;
}
p.border-blue {
    /* adds color using color name */
    border-color: blue;
}
p.border-green {
    /* adds color in RGB color format */
    border-color: rgb(0, 255, 0);
}
p.border-red {
    /* adds color in the hexadecimal color format */
    border-color: #ff0000;
}
Browser Output
CSS border-color Property as a Shorthand
We can use the border-color property to color one to all four sides of the border. For example,
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <link rel="stylesheet" href="style.css" />
        <title>CSS border-color</title>
    </head>
    <body>
        <p class="one-value">border-color: blue;</p>
        <p class="two-value">border-color: blue orange;</p>
        <p class="three-value">border-color: blue orange red;</p>
        <p class="four-value">border-color: blue orange red green;</p>
    </body>
</html>
p {
    /* adds border style to solid */
    border-style: solid;
    border-width: 8px;
    padding: 8px;
}
p.one-value {
    /* adds all side border colors to blue */
    border-color: blue;
}
p.two-value {
    /* sets top/bottom border to blue, left/right border to orange */
    border-color: blue orange;
}
p.three-value {
    /* sets top border to blue, left/right border to orange, bottom border to red */
    border-color: blue orange red;
}
p.four-value {
    /* sets top border to blue, right border to orange, bottom border to red, left border to green */
    border-color: blue orange red green;
}
Browser Output
CSS border-color Constituent Properties
border-top-color Property
The border-top-color property adds color to the top border of the element. For example,
p {
    border-top-color: blue;
}
Browser Output
border-right-color Property
The border-right-color property adds color to the right border of the element. For example,
p {
    border-right-color: blue;
}
Browser Output
border-bottom-color Property
The border-bottom-color property adds color to the bottom border of the element. For example,
p {
    border-bottom-color: blue;
}
Browser Output
border-left-color Property
The border-left-color property adds color to the left border of the element. For example,
p {
    border-left-color: blue;
}
Browser Output