In a longitudinal wave, the motion of the medium is parallel to the direction of the wave. This means that the particles move left and right which in turn makes the other particles start to oscillate.
The UNIA founded by Marcus Garvey has a constitution which defines red, black, and green as the Pan-African colours: red representing the noble blood that unites all people of African ancestry, the colour black for the people, green for the rich land of Africa..
For example, a peace flag reflects an aspiration and it only becomes a protest flag when used that way, otherwise, it remains just a peace flag. The Black Liberation Flag, also known as the Afro-American Flag, Pan-African Flag, and the UNIA Flag, is a symbol of African and African-American unity and pride. In the 1960s this flag became a symbol of Black liberation in the United States. This design was first adopted in 1920 as the official banner of the African Race at a meeting of the Universal Negro Improvement Association and African Communities League (UNIA) held in New York City.