But will it solve my sorting issue?That is my main problem. Why is there such a difference in the sorting on News and Concerts? The both group by date, but News group by month and Concerts by day which is useless in this case. Is it a bug that News folder is colored and Concert folder is gray-scaled as no icon is set in xml?The News package uses a page data folder but one adds it to a page as an application.
Judging from your screen dump, you've added your Concerts to a page as a page data folder. And it also looks like that your "Concerts" page data folder groups items by date. That's how you probably get the sorting and the icon you have issues with.
To follow the News example, you should add your "Concerts" to a page as an application (rigth click the page and click "Add Application"). Thus you'll get the sorting and the icon as expected.
For information about attaching your applications to trees in the C1 Console, please see How to Attach Console Applications