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..
Over a period of time humans have been able to identify the different colors and their meanings. Here is a brief description of the meanings associated with different colors: Black has always been regarded as a powerful color and therefore has been associated with authority and power.