Green crackers are those types of firecrackers made with reduction in shell size, elimination of ash usage etc. 

The reduced usage of raw materials means green firecrackers produce 30% to 35% less emissions compared to normal firecrackers. Its use is encouraged to mitigate the worst effects of air pollution.

For more relevant articles refer to the links given below:

• UPSC Environment and Ecology Questions
• International Union for Conservation of Nature (IUCN)
• UPSC Environment and Ecology