Unify a color-coded alert system

Abbloh Allkan series on paper, New York, USA, 2016

I read that China's Environmental Protection Ministry is demanding domestic cities to adopt a unified color-coded alert system

for air pollution. 

Cities have been instructed to use an alert system that uses blue, yellow, orange, and red to mark different levels of air pollution.  

I have created different standards for issuing air pollution alerts.