To be "Pro-Green", that is to say you are supporting the care of the environment. You support, fight for, and create awareness for environmental progress.
The terms Pro-Green Energy and Pro-Environment are also used.
"Americans need a smarter, cleaner energy policy that reduces our dependence on polluting energy sources, saves consumers money by significantly increasing energy efficiency and renewable energy, and protects public lands and coastal areas." (taken from http://www.lcv.org/president-and-congress/letters-to-congress/page.jsp?itemID=27693450)
"Reduce, reuse, recycle!", sang a Pro-Green activist, who I later found out to be Jack Johnson!