The Puerto Rico flag design is very similar to the Cuban flag and shows the close ties between patriots of both countries. The Puerto Rico flag has a red stripe instead of blue and a blue triangle instead of red.The original design of the flag used a sky blue shade for the left triangle and was associated with the Puerto Rican independence movement.
In 1952, the Commonwealth of Puerto Rico adopted the 1892 flag design but changed the sky blue to to the same dark blue of the U.S. flag. This is commonly used by the statehood faction who want Puerto Rico to become an official state of America.
The white star stands for the Commonwealth of Puerto Rico while the three sides of the triangle represent the three branches of the government.