Where in the world?
The flag of Saint Martin (French part) has a blue field with a white cross and a red border.

Saint Martin (French part)

Saint-Martin

Population: 38,659

Region: Americas

Subregion: Caribbean

Capital: Marigot

Top Level Domain: .mf, .fr, .gp

Currencies: Euro

Border countries

The flag of Sint Maarten has a red upper half with a white five-pointed star in the center, and a blue lower half.

Sint Maarten (Dutch part)

Population: 40,812

Region: Americas

Capital: Philipsburg
The flag of the Netherlands has three horizontal bands of color: red on the top, white in the middle, and blue on the bottom.

Netherlands

Population: 17,441,139

Region: Europe

Capital: Amsterdam