Skrevet live og uden test men måske ideen kan hjælpe :)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "
http://www.w3.org/TR/REC-html40/strict.dtd"><html>
<head>
<script type="text/javascript">
function sw(Obj) {
elm=document.getElementById("show");
elm.style.backgroundColor=Obj.style.backgroundColor; }
</script>
</head>
<body>
<table style="width: 300px; margin: 0px auto;">
<tr>
<td style="width: 100px; background-color: red;" onclick="sw(this);">Red</td>
<td style="width: 100px; background-color: blue;" onclick="sw(this);">Blue</td>
<td style="width: 100px; background-color: green;" onclick="sw(this);">Green</td>
</tr><tr>
<td colspan="3" id="show">Choose above</td>
</tr>
</table>
</body>
</html>
Mvh. Johan