What do the colours of the Cuba flag mean?

Blue: the three military districts the island was divided into. White: the purity of the independence cause. Red: the blood shed in the struggle; the triangle also stands for liberty, equality and fraternity.

How do you tell the Cuba flag from the Puerto Rico one?

The colours are swapped: Puerto Rico has red and white stripes with a blue triangle.

When was the Cuba flag adopted?

The current design dates from 1902, and its official ratio is 1:2.

The flag of Cuba

Five horizontal stripes, three blue and two white, with a red equilateral triangle at the hoist bearing a white five-pointed star.

Ratio 1:2 · current design adopted 1902

Cuba's and Puerto Rico's flags are the same design with the red and blue exchanged, and that is not coincidence: Puerto Rican revolutionaries adopted their version in 1895 in solidarity with the Cuban independence movement, deliberately inverting the colours of a flag already twenty years old. The Cuban design dates from 1849, was first raised at Cárdenas in 1850, and became official at independence in 1902. The triangle and the star are Masonic in origin, reflecting the movement's membership. Both flags are among the very few where the confusion is a designed reference rather than an accident.

Flags it gets confused with

Flag	How to tell them apart
Puerto Rico	The colours are swapped: Puerto Rico has red and white stripes with a blue triangle.

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
Lone star	La Estrella Solitaria — independence, and the hoped-for new state

Ratio: 1:2
Current design adopted: 1902
Colours: blue, white, red

Common questions

What does the flag of Cuba look like?: Five horizontal stripes, three blue and two white, with a red equilateral triangle at the hoist bearing a white five-pointed star.
What do the colours of the Cuba flag mean?: Blue: the three military districts the island was divided into. White: the purity of the independence cause. Red: the blood shed in the struggle; the triangle also stands for liberty, equality and fraternity.
How do you tell the Cuba flag from the Puerto Rico one?: The colours are swapped: Puerto Rico has red and white stripes with a blue triangle.
When was the Cuba flag adopted?: The current design dates from 1902, and its official ratio is 1:2.

Cuba Capital, area, population and currency
The flag of Puerto Rico Routinely mistaken for this one
Every flag with blue in it
The flag of United States Ratio 10:19
The flag of India Ratio 2:3
The flag of United Kingdom Ratio 1:2
The flag of France Ratio 2:3
The flag of Russia Ratio 2:3
The flag of Brazil Ratio 7:10
The flag of Australia Ratio 1:2
The flag of South Korea Ratio 2:3

Sources

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

How these figures are compiled and checked