border-color sets the color of the border.

        <style type="text/css"> 
        p { 
            border-width: 5px; 
            border-style: solid; 
            border-color: black; 
            HyperText Markup Language (HTML) is the main markup language for 
            displaying web pages and other information that can be displayed 
            in a web browser(From From Wikipedia, the free encyclopedia).
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See how to use the CSS color.

  HTML CSS Book