probably one or two. like for instance China's flag.
325 signs, not including the one without any flags.
YELLOW and RED
there are 5 Olympic rings and all the colours that are in the rings are the colours of the countries flags in whom are participating
The colours yellow, green and red are found on many national flags in Africa.
As far as I know theres 12, but some contain more colours aswell as red, black and white
The colours purple, red and blue are fairly evenly matched. Red and blue are the colours carried on many of the nations flags and national flags inspire courage. Purple is closely linked with dignity, representing an appreciation of the formality and gravity of the situation
The colours of Monaco's flag were the armorial colours of 'Grimaldi' in the middle ages.
Because the colours of the world flags had one of the colours on the Olympic rings
blue white red in equal vertical bars.
The Ethiopian flag is the oldest flag in Africa and its colours (red, yellow, green) have been adopted as the colours of the flags of many other African nations.
In theory, an infinite number. Unless you restrain what shapes the four colours can be, or how many of the colours can be used at one time. Not all shapes on flags have to be (a) formed by straight lines, (b) the same size.... look at the flag of Kiribati, Pakistan. Not all flags have to be rectangular - see the flag of Nepal. Confining oneself to just two colours - there are a vast amount of possibilities. Look at the number of countries that use just red and white.... Austria, Bahrain, Canada, Denmark, England, Georgia, Greenland, Indonesia, Japan, Monaco, Poland, Qatar, Singapore, Switzerland, Tonga, Tunisia, Turkey.... not to mention all the non-country flags that ue red and white, such as the Red Cross...
Two primary colours: blue and yellow.