As a symbol of independence from Spain, the Cuban flag has inspired a number of others, including those of Puerto Rico, the Philippines, and Catalan separatists.
Cuba’s flag was originally designed in 1849 in New York City by Venezuelan-Cuban General Narciso López and Cuban poet Miguel Teurbe Tolón to symbolize the effort to have the US annex Cuba from Spain. The star represented the new star to be added to the US flag for a hoped-for State of Cuba. Whitney Smith writes: “The red triangle stood for strength and constancy, but it may also have reflected Masonic influences (triangles are Masonic symbols for equality and were found in a number of other flags in the former Spanish empire).”
Puerto Rico’s flag, an adaptation of López’ flag, was first presented in 1892 to the PR Revolutionary Committee in New York City, which officially adopted it in 1895. There are differing accounts of its creation; e.g., Antonio Vélez Alvarado said it came to him as an after-image of a Cuban flag he had been staring at on the wall of his Manhattan apartment. (Actually, however, the perceptual after-images of red and blue are green and yellow, respectively, not blue and red.) Different shades of blue are in use, sometimes representing different positions regarding PR’s future status; the territorial government’s website shows both Royal Blue and Old Glory Blue versions.
Puerto Rico’s flag is easily confused with Cuba’s (and, by the way, is identical to a Norwegian shipping company’s). One way to keep it straight is to note that unlike Cuba’s it has red and white stripes, just like that of the US, in which Puerto Rico has commonwealth status. Another way is to remember this meme:
The “three stars and a sun” flag of the Philippines, like that of Puerto Rico, dates from the time of the Spanish-American War. It was designed by revolutionary leader Emilio Aguinaldo in 1897, while he was exiled in Hong Kong. Although the influence of the Cuban flag is often claimed with respect to its design and colors, and is plausible given the general context of the breakup of the Spanish empire that started in Cuba and spread to the Philippines, there does not appear to be definitive evidence for this. The equilateral triangle was used in both as a Masonic symbol for equality (see the Whitney Smith quote above), but this may have been coincidental, as the Philippine revolutionary group Katipunan was masonic in its origins. The evidence may be circumstantial, but some level of inspiration from López’ Cuban flag seems likely.
The Catalan separatists’ Estelada was designed by Vicenç Albert Ballester i Camps in 1918. Ties between independent Cuba and the separatists were deep and longstanding (and Cuba today still has a small Catalan community of 3600). Twelve years earlier, the Centre Catalanista de Santiago de Cuba (Catalanist Center of Santiago de Cuba) had been established. In the 1928 Catalan Constitution of Havana, exiled separatists declared both independence and the Estelada to be the national flag. In the current Catalan independence movement, the “classic” white-star-on-blue-triangle flag is very much back in vogue, alongside a large number of variants.