Template:Skin/Ur
Use hexadecimal color codes to edit the range. You can add or remove as many colors as you want -- just make sure all four rows have the exact same color codes.
If you want a blank skin box: Template:Skin.
Check out how it's used here.
box-shadow: 0px 0px 10px #777777; height: 25px;
background: -webkit-linear-gradient(left, #eaeaea, #1c1c1c, #4f2c16); /* For Safari 5.1 to 6.0 */
background: -o-linear-gradient(left, #eaeaea, #1c1c1c, #4f2c16); /* For Opera 11.1 to 12.0 */
background: -moz-linear-gradient(left, #eaeaea, #1c1c1c, #4f2c16); /* For Firefox 3.6 to 15 */
background: linear-gradient(left, #eaeaea, #1c1c1c, #4f2c16); /* Standard syntax */