Vexillology is the scholarly study of flags. (So says Our Lady of the Wikipedia.) I love logos, and flags are like logos. It's corporate identity for a nation's government. In fact, there are five basic principles:
1. Keep It Simple: The flag should be so simple that a child can draw it from memory.The related part of #5 explains all those crazy Scandinavian flags I can't tell apart.
2. Use Meaningful Symbolism: The flag’s images, colors, or patterns should relate to what it symbolizes.
3. Use 2–3 Basic Colors: Limit the number of colors on the flag to three, which contrast well and come from the standard color set.
4. No Lettering or Seals: Never use writing of any kind or an organization’s seal.
5. Be Distinctive or Be Related: Avoid duplicating other flags, but use similarities to show connections.
(Shown is the glorious banner of my Nation States nation, a proud member of the region of Decipheria, known as Shocho. Oops, I broke #4.)