$count_rows = 0;
while ($row = mysql_fetch_array($query))
{
$campo = $row['campo'];

if ($count_rows%2==0)
{ $row_color="#ff0000"; }
else
{ $row_color="#0000ff"; }
echo "<tr bgcolor=\"$row_color\">";
echo "<td>$nome</td>";
echo "</tr>";
$count_rows++;
}


Cmq se stai usando i css non ha senso poi mettere bgcolor.