What do the colours of the Mexico flag mean?

Green: originally independence; now commonly read as hope. White: originally the purity of the Catholic faith; now unity. Red: the blood of the heroes of independence.

How do you tell the Mexico flag from the Italy one?

Italy has no coat of arms, a shorter 2:3 ratio and a lighter green.

When was the Mexico flag adopted?

The current design dates from 1968, and its official ratio is 4:7.

The flag of Mexico

Three equal vertical bands of green, white and red, with the national coat of arms — a golden eagle on a cactus, devouring a snake — centred on the white.

Ratio 4:7 · current design adopted 1968

Mexico

Field and colours only. Not shown: the eagle devouring a snake, centred on the white band.

The colour meanings were officially reinterpreted after the 1860s reform laws stripped the flag of its religious reading, so a Mexican textbook and a nineteenth-century source will give different answers and both are correct for their period. The eagle has been redrawn many times; the current version was fixed in 1968, in time for the Mexico City Olympics. The snake is a later addition to the founding legend — the earliest codices show the eagle on the cactus alone, sometimes holding the Nahuatl glyph for war rather than a serpent. At 4:7 the flag is noticeably longer than the Italian tricolour it is otherwise mistaken for.

Flags it gets confused with

Mexico

Field and colours only. Not shown: the eagle devouring a snake, centred on the white band.

Italy

Drawn at each flag’s own official ratio, which is itself the difference in some of these pairs.

Flag	How to tell them apart
Italy	Italy has no coat of arms, a shorter 2:3 ratio and a lighter green.

What the colours mean

Flag laws usually specify a Pantone chip, a CMYK mix or just a colour name. Converting any of those to sRGB is lossy, which is why published hex values disagree.

The symbols on it

What	What it stands for
Eagle, cactus and serpent	The sign the Mexica were told to look for when founding Tenochtitlan, on the site of modern Mexico City

Ratio: 4:7
Current design adopted: 1968
Colours: green, white, red

Common questions

What does the flag of Mexico look like?: Three equal vertical bands of green, white and red, with the national coat of arms — a golden eagle on a cactus, devouring a snake — centred on the white.
What do the colours of the Mexico flag mean?: Green: originally independence; now commonly read as hope. White: originally the purity of the Catholic faith; now unity. Red: the blood of the heroes of independence.
How do you tell the Mexico flag from the Italy one?: Italy has no coat of arms, a shorter 2:3 ratio and a lighter green.
When was the Mexico flag adopted?: The current design dates from 1968, and its official ratio is 4:7.

Mexico Capital, area, population and currency
The flag of Italy Routinely mistaken for this one
Every flag with green in it
The flag of India Ratio 2:3
The flag of Brazil Ratio 7:10
The flag of Ireland Ratio 1:2
The flag of South Africa Ratio 2:3
The flag of Jamaica Ratio 1:2
The flag of Pakistan Ratio 2:3
The flag of Palestine Ratio 1:2
The flag of Portugal Ratio 2:3

Sources

The World Factbook — Central Intelligence Agency (Public domain (US Government))

How these figures are compiled and checked