Three vertical stripes, side by side. This is the layout France itself uses, and it’s the one most directly tied to the Revolution, since the design was meant to be read the same way regardless of which side of the flagpole you were standing on. From France, it spread fast: Italy adopted a version in 1797 within a decade of the French flag’s own adoption, and it kept spreading through the 19th and 20th centuries as new nations across Africa and the Americas formed and needed a flag of their own.
That spread is exactly why so many vertical tricolours end up looking alike. Romania and Chad fly the same blue, yellow, and red in the same order, by pure coincidence. Mali and Guinea fly the same green, yellow, and red, in reverse order from each other, this time not by coincidence at all, but because both drew on the pan-African colors during their own independence movements.
Below, every country flying a vertical tricolour, linked through to the story behind its specific colors.
Vertical Tricolours
France · Italy · Ireland · Romania · Chad · Mali · Guinea · Côte d’Ivoire · Belgium · Nigeria · Cameroon · Senegal · Moldova · Andorra · Mexico · Afghanistan · Mongolia · Barbados · Canada · Guatemala · Saint Vincent and the Grenadines · Peru