Green Paper
noun [ C ] uk/ˌɡriːn ˈpeɪ.pər/ us/ˌɡriːn ˈpeɪ.pɚ/
绿皮书（尤指英国政府供民众对修改法律或制定新法律提出建议的文件）
in various countries, a government document that anyone who is interested can study and make suggestions about, especially before a law is changed or a new law is made
Compare: White Paper