<?php
   $sqln = mysql_query("SELECT * FROM post ORDER BY id DESC LIMIT ".$inicio.",".$max."");
   $num = mysql_num_rows($sqln);
   for($i = 0; $i < $num; $i++){
     $tituloP = @mysql_result($sqln, $i, "titulo");
     $n = $i + 1;
     $d = $i % 2;
     if($d == 0){$cor = "cinza";}else{$cor = "claro";}
     print '<tr class='.$cor.'><td> align="center">'.$tituloP.'</td><tr>';
   }

?>

<?php
   $sqln = mysqli_query($conn, "SELECT * FROM post ORDER BY id DESC LIMIT ".$inicio.",".$max."");
   mysqli_close($conn);
   while($num_q = mysqli_fetch_array($sqln)){
      $tituloP = $num_q['titulo'];
      print '<tr class=' /*COR*/'><td align="center">'.$tituloP.'</td><tr>';
   }
?>

$index = 0;
while(...) {

    if($index%2==0){ echo 'class="branco"'; }
    else { echo 'class="cinza"'; }

    $index++;
}