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..
Black was also used as a standard color for hair and to represent the skin colour of people from the south â Nubians and Kushites. White (Ancient Egyptian name 'hedj') was the color of purity, sacredness, cleanliness, and simplicity. Tools, sacred objects, and even priest's sandals were white for this reason.