The app helps you stay up to date on the quality of air in Slovenia.
The data is fetched from http://www.arso.gov.si.
There are information about S02, CO, O3, NO2 and PM10 particles listed for most of the larges cities. PM10 is the main attribute that gives cells a slight tint.
There is also an Apple Watch companion app that lists PM10 data. It includes a complication that shows PM10 particles data for a preselected city.