Hi, not discouraging others from answering here, but while you're waiting you might be interested in this recent answer by u/Aleksx000 in Why do many Arab nations have red, white and green in their flags? Why do many African nations have red, green and yellow?

or the FAQ section Why do flags have similar colours?:

• Why are red, white and blue common national colors?

• Why do so many countries use the colors red, white, and blue for their flags?

• Why did countries in the British Empire like Canada, British India, and the Union of South Africa have red British ensign flags as opposed to the blue ensign flags of Australia and New Zealand?

• Why were British colonial flags different colours? (I.E: Canada's was red while Australia's was blue)

• Why did the American Flag retain the red, white, and blue of the Union Jack?

• Why does Malaysia's flag look similar to USA's flag? Is there some sort of code for national flag designing?

• Why are so many national flags so similar?