The third parameter of hsl() defines the lightness. 0% means black, and 100% means white:
<h2 style="background-color:hsl(0, 100%, 0%); color: hsl(0, 100%, 100%);"> <h2 style="background-color:hsl(0, 100%, 25%);"> <h2 style="background-color:hsl(0, 100%, 50%);"> <h2 style="background-color:hsl(0, 100%, 75%);"> <h2 style="background-color:hsl(0, 100%, 90%);"> <h2 style="background-color:hsl(0, 100%, 100%);">