What is the only country in the world that has a flag with just one color and no design or symbol?

The only country that once had a completely one-colored flag with no design or emblem was Libya. From 1977 to 2011, under the rule of Muammar Gaddafi, Libya adopted a plain green flag. The green color symbolized Islam, which is the nation’s dominant religion, and also represented Gaddafi’s political philosophy outlined in his Green Book. This flag was unique because no other national flag in the world consisted of a single color without any stripes, stars, or symbols. After Gaddafi’s fall in 2011, Libya reverted to its red, black, and green flag with a white crescent and star, ending the era of the world’s only single-colored national flag.