If you want it with colour use the code below and change where it says COLOURHERE to have your own colour.
<hr color="#COLOURHERE">

If you want a border style use the code below here.
And these are the border styles that can be used: Inset, Outset, Ridge, Groove, Dashed, Dotted, Solid and Double.
<hr style="border-style: BORDER STYLE; border-width: 1" color="#000000" size="1">