The calendar is colored after the number of stars you rate the day.
No stars is indicated with white background.
One to six stars is marked red.
Seven to eleven stars is marked yellow and twelve to twenty stars is marked with green.
In that way you get an easy overview of the status of days in month.
There are five summaries where the first shows total numbers of stars per day and month. The four others show number of stars for each category and day for a month.