In the photo, a red and blue LED are attached to a string and spun around in a circle. The red LED is attached on the shorter side of the string, creating the effect that makes it look like the red LED is inside the blue LED. The camera is on the floor and the shutter is kept open for about 12 seconds.

Where the red intersects with the blue light, magenta light is produced. This is a property of additive color mixing. Additive color mixing is a property only light exhibits in which light mixes together to produce different colors. This is also true for white sunlight, which is a combination of the whole spectrum. For computer screens, what appears to be white light is a combination of red, green, and blue LED’s in equal proportions and maximum brightness. These three colors are primary colors, which cannot be produced by mixing other colors, and when mixed in equal proportions produce white light. Equal proportions are important because mixing light in different amounts produces different colors. For example, one part red, two parts green, and zero parts blue produces lime green. To find the proportions that produce a desired color of light (excluding brightness), a color triangle can be used.