This question is asking for opinions since beauty is in the eye of the beholder, so please do not remove another person's good answer even if you disagree with their opinion. There is no right or wrong answer, just opinions of preference. Place your opinion below those before yours.
Belize has 8 colours on their national flag
It depends on whose flag it is. But the flag has the number and the base color of the car on it.
Lybia has a green flag
Libya has only green colour on her flag.
The Libya flag is the only country to have a flag with only one color. The flag is solid green. It is green because green is the national color of libya showing their devotion to islam.
The flag of Egypt's colors are: ~Red ~White ~ And Black
blue and white
LIBYA
Libya
Barbados
Prior to the Arab Spring War in 2011, the national flag of Libya used to have only one color; green. More specifically, it consisted of a simple green field with no other characteristics. Also, many signal flags are just one color. Then, of course, the flag of surrender is but one color; white. Currently, there is no national flag with only one color.
The flag for the country of Belarus is red and green in color. The flag also has a red and white ornament design on the staff side of the flag.
TURKEY Japan and MANY more!