$col = "white";

while($a1 = mysql_fetch_array($r1))
{
	if($col == "white")
	{
		$col = "dddddd";
	}
	else
	{
		$col = "white";
        }

	echo "<tr bgcolor=$col>";
        echo "<td><a href=\"#\">Teste</a>";
        echo "</td><td align=center>Teste</td></tr>";
}