Tinymce doesn't use my theme's css styleheet

i’ve added these lines to my functions.php:

// Connect the WordPress post editor to your custom stylesheet
function my_theme_add_editor_styles() {
 add_editor_style( 'editor-style.css' );
add_action( 'admin_init', 'my_theme_add_editor_styles' );

Then i got the message in Design > Editor:

WordPress Wiki Theme: Stylesheet für WYSIWYG-Editor (editor-style.css)

where i added this link to my current theme’s css document which is in the same directory like the editor-style.css

@import url( ‘style_blue.css’ );

/* Add overwrites as needed so that the content of the editor field is attractive and not broken */
body { padding: 0; background: #fff; }

But i get still only the wp-content.css sytle while editing e.g. a new page.

What am i doing wrong?