What is Calendar Legend block for? enabled but shows nothing Playing around with Calendar + Date.

There is a block called Calendar Legend, but shows nothing. What is it for? Where should I configure?, I checked the block configuration and views setup, no clues. 

Thanks.
The Legend is used on the large calendar page view to help denote between content types or taxonomy. You can set the colours of the content types or taxonomy by editing the view at /admin/structure/views/view/calendar/edit and select Format > Show > Settings