Color is the thing we perhaps notice most about light in the world around us. But why we see colors the way we do all has to do with light. The reason something appears to be the color that does is that the object is absorbing all the other colors of light except the ones we see, which are reflected back to our eyes. If something absorbs all the colors, it appears black, if it reflects everything, it appears white. Color comes from what is called the visible spectrum of light. This spectrum goes from red to orange to yellow to green to blue to indigo to violet, all the major colors of the spectrum, and everything in between. An easy way to remember this order is to remember Roy G. Biv, much like the colors of the rainbow. Scientists measure the wavelengths of light in this spectrum in nanometers or billionths of a meter. Red has the longest wavelength, and violet has the shortest. So, what color we see depends on the wavelength of the light we absorb into our eyes. The primary colors are red, green, and blue, from these colors, every other color can be made. This is how televisions, movies, and other projection screens work, they only actually project red, green, and blue, but combine them in little dots called pixels, so that the right shades and images are formed on the screen. But don't confuse this with paint, pigments mix differently than light, and primary pigments can vary, though red, yellow, and blue are fairly common ones. Color also varies on the amount of light present in the area, which is why things can appear different in different light, and with different reflectors around them. A prime example is people with blue eyes, depending on the clothes they are wearing, the shade of blue in their eyes can lighten or deepen, depending on which light waves are being reflected by the clothes they are wearing. Outside of the visible spectrum, there are many non-visible forms of light, infra-red which is used in remote controls, ultraviolet light, used in black lights, x-rays used in x-ray machines, and gamma rays and other various forms of radiation given off from the sun.