The flag of the Union of Democratic Planets is a grey flag with three colored circles of blue, yellow, and green, placed in the canton. The three circles represent the three founding planets of the UDP, while the grey coloring was used to represent the full area of the Union (i.e., Space).
The grey coloring was chosen for the flag to distinguish itself from the blackness of space (as opposed to the commonly used white). The three circles of blue, green, and yellow represent the three founding planets (Vellamo, Dazbog, and Izanami respectively). The colors were chosen based on culture and planetary color (the bayous of Dazbog give the planet a green tint, the deserts of Izanami give it a gold tint, and the snow-capped mountains of Vellamo give it a bluish tint). The three circles are positioned roughly the same locations that the planets are located between one another (with the bottom roughly representing the location of the galactic center).