Highlight data Filter

You will use PHP to check if the date has already passed (you have not clarified where the date is to be checked, I'm assuming it's in "LifeValue"):

if (strtotime($exibe['AlvaraValidade']) < time()) {
    // Coloca uma cor diferente
}

Being specific to your case, putting the Red color on the date:

echo "<tr><td>Alvara Validade:</td>";
echo"<td>";
if ($exibe['AlvaraValidade']) { 
    if (strtotime($exibe['AlvaraValidade']) < time()) {
        echo '<span style="color:red">'.$exibe['AlvaraValidade'].'</span>';
    } else {
        echo $exibe['AlvaraValidade'];
    }
} else { 
    echo 'N/D';
} 
echo "</td></tr>";

It has an important detail: You will be using the function strtotime () to transform a string into timestamp. This string needs to be in the format that is usually in the database, which is for example: 2014-03-24 13:21:00 or only the date 2013-03-24, so it can compare with the current date that is obtained with time () in an integer timestamp. If the date is in the Brazilian format for example, you need to change it to the d-m-Y format

You can also put the conditional directly into the SQL query, which will abstract your logic a bit more:

SQL:

SELECT 
    id, nome, morada, etc, IF (datacadastro < '2014-02-01', 'ultrapassada', '') AS ultrapassada
FROM
    tb_detalhe_trabalhador 
    INNER JOIN tb_trabalhador on tb_detalhe_trabalhador.id = tb_trabalhador.id 
    INNER JOIN tb_equipamentos on  tb_detalhe_trabalhador.id = tb_equipamentos.id

PHP:

while($exibe = mysql_fetch_array($qr)){
    echo("
        <table>
            <tr class='{$exibe['datacadastro']}' >
                <td >{$exibe['datacadastro']}</td>
                <td>{$exibe['morada']}</td>
                <td>{$exibe['nome']}</td>
            </tr>
        </table>"
    );
}

CSS:

tr.ultrapassada {
    background: red;
}

In this rustic example, all lines with dates before 2014 / February will be highlighted in red.

Other options could be (in the database):

IF (DATEDIFF(NOW(), c.datacadastro) > 30, 'mais-de-30-dias', '') AS maisDe30
IF (DATEDIFF(NOW(), c.datacadastro) < 7, 'ultimos-7-dias', '') AS ultimos7dias

In addition, putting the conditionals in the database, the performance will be much faster than in PHP.