About the colors, symbols, symbolic meanings and interesting facts of the national flag.

Red: Blood (of struggle for independence, sacrifice, revolution), bravery, strength, valor.
White: Peace, purity, snow, honesty.
Blue: Sky, water, perseverance, justice, truth, vigilance.
Green: Nature, agriculture, fertility, Islam, hope.
Yellow/Gold: Sun, wealth, energy, justice, the desert.

Astronomical: Stars (often representing states or provinces, e.g., USA, Australia, China, Brazil), suns (e.g., Argentina, Japan, Kazakhstan), moons (e.g., Turkey, Pakistan, Singapore).
Religious: Crosses (Nordic crosses, Switzerland, Greece), crescents (Islamic nations), the Dharma Chakra (India).
Political/Ideological: Stars (communism/socialism - China, Vietnam, Angola), hammers and sickles.
Natural: Cedars (Lebanon), maple leaf (Canada).

Stripes: Very common. They can represent the original colonies (USA), the provinces of a country (Malaysia), or principles like liberty (France's tricolore).
Crosses: The Nordic Cross is used by all Scandinavian countries (Sweden, Norway, Denmark, Finland, Iceland).
Triangles: Often symbolizing mountains or forward progress (e.g., Czech Republic, Bahamas).
Circles/Discs: Representing the sun (Japan, Bangladesh) or the moon (Laos).

The study of flags is called vexillology (from the Latin vexillum, meaning "flag"). Vexillologists have established key principles of good flag design, popularized by the North American Vexillological Association:
A: Keep It Simple. A child should be able to draw it from memory.
B: Use Meaningful Symbolism. The colors, patterns, and symbols should reflect the nation's values, history, or people.
C: Use 2–3 Basic Colors. Limit the palette for clarity and cost-effective reproduction.
D: No Lettering or Seals. Words are hard to read and seals are complex details best left for official documents.
E: Be Distinctive or Be Related. A flag should be unique or clearly show its cultural/historical ties (e.g., the Pan-African or Pan-Arab colors).

Tricolours: The most common format, originating with the Netherlands and popularized by the French Revolution. Horizontal: Germany, Russia, Netherlands, Austria, Serbia. Vertical: France, Belgium, Italy, Ireland, Ivory Coast.
Pan-Arab Colours: Red, black, white, and green. Seen in the flags of Egypt, Iraq, Jordan, Kuwait, Sudan, Syria, UAE, and Yemen. They symbolize Arab unity and independence.
Pan-African Colours: Red, yellow/gold, and green (sometimes black). They originate from the flag of Ethiopia, one of the oldest independent African nations. Examples: Ghana, Senegal, Mali, Cameroon, Kenya.
Pan-Slavic Colours: Red, blue, and white. Adopted from the flag of Russia. Examples: Slovakia, Slovenia, Czech Republic, Serbia, Croatia.
Commonwealth Flags: Several former British colonies feature the Union Jack in the canton, most notably Australia and New Zealand, which has led to ongoing debates about changing their flags.
Islamic Symbols: Many flags of Muslim-majority countries feature a crescent moon and star (Turkey, Pakistan, Tunisia, Algeria, Malaysia) or the color green.
Communist Flags: Often feature a red field with a yellow star or other socialist symbol (China, Vietnam, North Korea, Angola, Mozambique).

Oldest Flag: Denmark's Dannebrog is the oldest continuously used national flag, legendarily dating back to 1219.
Only Non-Quadrilateral Flag: Nepal's flag is made of two overlapping triangles, representing the Himalayas and the two main religions, Hinduism and Buddhism.
Flags That Are Square: Only two countries have square flags: Switzerland and the Vatican City.
Most Colors: The flag of South Africa is one of the most colorful with six: red, white, blue, green, yellow, and black.
Mirror Image Flags: The flags of Poland (white top, red bottom) and Indonesia (red top, white bottom) are mirror images of each other. Monaco's flag is identical to Indonesia's.
Flags Within Flags: The flag of the United Kingdom (the Union Jack) is a combination of the crosses of St. George (England), St. Andrew (Scotland), and St. Patrick (Ireland).
Changing Flags: National flags can change. South Africa changed its flag in 1994 after the end of apartheid. Rwanda changed its flag in 2001 to distance itself from the 1994 genocide.
Malaysia's flag changes slightly every time a new state is added to the federation (the stripes represent the states).