Green splits mainly into two traditions. Across the Muslim world, it’s tied closely to Islam itself, associated with the Prophet Muhammad and used as a marker of Islamic identity on flags from North Africa through the Middle East and into South Asia. Elsewhere, especially across Africa and Latin America, green points somewhere more literal: forests, farmland, and the fertility of the land itself.
Islamic symbolism
Saudi Arabia · Pakistan · Libya · Mauritania · Algeria · Bangladesh · Turkmenistan · Iran · United Arab Emirates · Comoros
Pan-African colors, forests and agriculture
Senegal · Mali · Guinea · Ghana · Cameroon · Benin · Togo · Burkina Faso · Nigeria · Zimbabwe · South Africa · Gabon · Congo, Democratic Republic of the · Ethiopia · Kenya
Land, agriculture, and independence movements elsewhere
Mexico · Brazil · Ireland · Italy · Hungary · Bulgaria · Lithuania · [Belarus, if added later] · India · Zambia · Suriname · Jamaica
Everywhere else green shows up prominently
South Sudan · Portugal · Bolivia · Cape Verde · Madagascar · Guinea-Bissau · Equatorial Guinea