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..
As a means of presenting examples of the use of the colors red, black, and green in African American culture, this post includes a sound file of The Kwanzaa Song by Teddy Pendergrass is included in this post.