The flag was first flown in 1821, when insurgent leader Miguel Hidalgo y Costilla unfurled it as a symbol of the Mexican War of Independence. Historians believe that this flag design was influenced by the French Tricolor, but the colors were distinctively Mexican.
This new country needed a flag to represent its ideals and heritage. Much like the French tricolour, the colours were symbolic of what the people stood for.
Green, white and red were the colours used by insurgents under Miguel Hidalgo during the war of independence. While these unique colours made up the flag during this stage of history, they are not the true unofficial symbolism of these colours as used in flags.
Related: Red Gradients