One way I learned from my parents for keeping Planet Earth "green" for other generations, is recycling used up materials, or materials that we simply do not want in our house.
Another way is to stop any electricity waste that we are doing, and stop wasting water like it's an infinite source. Water is finite natural resource, that we need to keep by us forever, or else future generations will not have it and they will not be able to prosper like us.
The final way that we can keep our planet "green" is by stopping gas emissions from factories, and having "green" days, where all the factories close, and no one uses electricity.