The border-color property sets the color of all four borders of an element, and can have from one to four values.

/* set all 4 borders to red */
div {
    border-color: red;
}

/* set top and bottom borders to red and both side borders to blue */
div {
    border-color: red blue;
}

/* set the top border to red, the side borders to blue, and the bottom border to green */
div {
    border-color: red blue green;
}

/* set the top border to red, the right side border to blue, the bottom border to green, and the left border to purple */
div {
    border-color: red blue green orange;
}

Default value	black
Inherited values	no
Can it be animated?	yes

These are the allowed values.

Value	Description
color	Specifies the color of the border (default color is the current color of the element)
transparent	Specifies that the border color should be transparent
initial	Sets this property to its default value
inherit	Inherits this property from its parent element

The HTML element can also be styled using JavaScript and the element’s id.

document.getElementById('my_div').style.borderColor = 'red blue';

<button onclick='my_function()'>Click Here</button>

<script>
function my_function() {
    document.getElementById('my_div').style.borderColor = 'red blue';
}
</script>

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