Index Color is a process where a design with lots of colors is reduced down to a limited color palette using Adobe Photoshop’s Index Color Mode. The process of “indexing” a design also converts the design to a diffusion dither random square dot (all the dots are the same size) pixel pattern rather than halftone dot patterns. The design is separated and printed directly from Photoshop, or the file is brought into a drawing program for additional text or graphic elements. You actually pick colors from within the design for Photoshop to use as your master Color Palette. It takes these colors and creates an image using just the colors you pick. All secondary colors are made using the colors you pick for your color palette.