When light hits an object it can either pass through, reflect, be absorbed or (most interestingly) be refracted/dispersed. This refraction is most commonly shown by a white light hitting a prism. Depending on the angle different colors will appear. Neat!
When many different colors and light sources come together in the form of lines, arrows, stars and other fragments all colliding in a nebula of light, you get one impressive YouTube background! Wear this one with pride and don’t forget to pick up the matching YouTube Avatar.