The Mexican flag consists of three stripes green, white, and red with an emblem in the center. The overall general design of the Mexican flag has been the same since 1821, but the current flag was officially adopted in 1968.
The emblem in the center of the flag is the image of an eagle holding a large snake. Below the eagle is cactus a rock and a lake. The Aztecs had a legend that their gods had instructed them to found a city where they saw an eagle with a snake. According to the legend this is the city that became Mexico City.
Originally the three colors represented green for independence from Spain, white for the Roman Catholic religion, red for union between Europe and the Americans. Overtime the meanings were changed and the current official definition of the flag is doesn’t assign a meaning to the colors. Generally the colors are now known to be green for hope, white for unity or purity, and red for religion or blood of heroes.
Up until 1968 Mexico used the tri-color flag without the emblem for some things. However when they hosted the 1968 summer Olympics, this presented a problem because it was identical to the Italian flag. This led to the current definition that requires the emblem.
In 1995 the legal definition of the Mexican flag was changed once again because it didn’t allow for the reverse side of the flag to allow the eagle to face right instead of left as it is on the front of the flag. After the 1995 change, an official flag can now be viewed from both sides.