There is a single flag matching these criteria: Flag of Estonia.
Blue in Flags
Blue is often used in flags to represent freedom, peace, loyalty, and the sky or sea. Many nations with coastlines or maritime traditions feature blue, such as Greece and Argentina. In other cases, blue reflects stability, truth, and justice, as seen in the flags of the United States and the European Union. The calming effect of blue makes it one of the most versatile and widely respected colors in vexillology.
Black in Flags
Black in flags often conveys strength, determination, and resilience. It can also symbolize mourning, remembrance, or the struggle of a people. In some African nations, black represents the heritage and identity of the people. Historically, black has also been associated with resistance or defiance. Flags like those of Kenya, Angola, and Estonia use black as a bold statement of endurance and pride.
