if is page conditional css not working

I want to change my contact form color in my website but it should be different color in every page so I decided to create a if is page conditional css. I put this code in my header.php but it didn’t work

<style type="text/css">
<?php
if(is_page('6')){ ?>

.form {
    color: #FFFFFF !important;
}

<?php
} else {?>

.form  {
    color: #000000 !important;
}

<?php
}
?>
</style>