在WordPress 3.5中，这个钩子适合我：

add_action( \'print_media_templates\', \'wpse_75746_print_style_35\' );

function wpse_75746_print_style_35()
{
    ?>
    <style>
        .media-modal-content, .media-sidebar {
            background: #FFF2D4 !important;
        }   
    </style>
    <?php
}

add_action( \'admin_print_styles-media-upload-popup\', \'wpse_75746_print_style_342\' );

function wpse_75746_print_style_342()
{
    ?>
    <style>
        #media-upload {
            background: #FFF2D4 !important;
        }
    </style>
    <?php
}