Color printing yellow (minus-blue) overprinted by magenta (minus green) yields red. Where all three inks may overlap, almost all incident light is absorbed or subtracted, yielding near black, but in practical terms it is better and cheaper to use a separate black ink instead of combining three colored inks. The secondary or subtractive colors cyan, magenta and yellow may be considered "primary" by printers and watercolorists (whose basic inks and paints are transparent). Two graphic techniques are required to prepare images for four-color printing. In the "pre-press" stage, original images are translated into forms that can be used on a printing press,
Color printing printing until the 1930s. Typically color separation is the responsibility of the color separator. This includes cleaning up the file to make it print ready and creating a proof for the prepress approval process. The process of color separation starts by separating the original artwork into red, green, and blue components (for example by a digital scanner). Before digital imaging was developed, the traditional method of doing this was to photograph the image three times, using a filter for each color. However this is achieved, the desired result is three grayscale images, which represent the red, green, and blue (RGB)