There is A Reference to The Aztecs on the Mexican Flag

Mexico's national flag is a green, white, and red vertical tricolor with the national coat of arms charged in the center of the white stripe. These three colors were selected by Mexico following independence from Spain during the country's War of Independence and subsequent First Mexican Empire, even if their meanings have altered through time. A point quite interesting is there is a reference to the Aztecs on the Mexican flag. With the people who not have a wide knowledge about history, this is one of the interesting facts about the Aztecs and their empire

Mexico's national army is represented by the colors red, white, and green. The Mexican coat of arms is the major emblem, which is based on the Aztec sign for Tenochtitlan (now Mexico City), the Aztec Empire's capital. It is said that an eagle perched on a prickly pear cactus devoured a rattlesnake. The artwork depicts the founding of Tenochtitlan, the Aztec capital city. The roaming Aztecs would know where to build their new city if they saw an eagle perched on a cactus, according to mythology. They did see the image, but it was on a little island in the midst of Lake Texcoco, which seemed improbable. The Aztecs constructed their city by connecting a series of miniature garden islands with causeways.

The serpent was later added to the account by the Spanish, based on a mistranslation of Aztec literature. Snakes were adored by the Aztecs as symbols of wisdom and creation, but the image was reinterpreted by the early missionaries. To Europeans, it would come to symbolize the struggle between good and evil in Mexico, as well as the success of Christian evangelization.