Where in the world?
The flag of the Congo has a green field with a yellow diagonal stripe from the lower hoist-side to the upper fly-side.

Congo

République du Congo

Population: 5,518,092

Region: Africa

Subregion: Middle Africa

Capital: Brazzaville

Top Level Domain: .cg

Currencies: Central African CFA franc

Border countries

The flag of Angola has two horizontal bands of red and black with a yellow half gear wheel crossed by a machete and crowned with a star.

Angola

Population: 32,866,268

Region: Africa

Capital: Luanda
The flag of Cameroon has three vertical stripes of green, red, and yellow with a yellow star in the center.

Cameroon

Population: 26,545,864

Region: Africa

Capital: Yaoundé
The flag of the Central African Republic has four horizontal stripes of blue, white, green, and yellow with a red vertical stripe in the center and a yellow five-pointed star in the upper hoist-side corner.

Central African Republic

Population: 4,829,764

Region: Africa

Capital: Bangui
The flag of the Democratic Republic of the Congo has a sky blue field with a yellow star in the upper hoist-side corner and a diagonal red stripe with a thin yellow border from the lower hoist-side to the upper fly-side.

Congo (Democratic Republic of the)

Population: 89,561,404

Region: Africa

Capital: Kinshasa
The flag of Gabon has three horizontal stripes of green, yellow, and blue.

Gabon

Population: 2,225,728

Region: Africa

Capital: Libreville