How to add a button to ACF tiny MCE editor

问题

How can i add a button to ACF WYSIWYG editor ( for example 'text color' button ). i tried this code but it doesn't work :(

add_filter( 'acf/fields/wysiwyg/toolbars' , 'dw_add_buttons_to_acf_wysiwyg_editor'  );
function dw_add_buttons_to_acf_wysiwyg_editor( $toolbars ){
    $toolbars['Full'][2][] = 'forecolor';

    return $toolbars;
}

来源：https://stackoverflow.com/questions/27462326/how-to-add-a-button-to-acf-tiny-mce-editor