A color palette is a function which maps integers to colors.
When only a few colors are needed, an effective way to save on storage costs is to store the needed colors in a table, and then refer to them using small integers. Such a color system is called indexed, and the array holding the colors is called a palette (in reference to arts). Back in the early days of computer graphics memory space was in premium, necessitating the use of an indexed color system. While the first system allowed only 2 colors (monochrome), the later systems allowed subsequentially larger palettes to be used: 4 (CGA standard), 16 (EGA standard), and finally 256 (VGA standard). These numbers of colors correspond to 2, 4, and 8 bits for the size of the indexing integer.
Nowadays color indexing is primarily of interest in the hopes of creating image files of small size when there are only a few colors. Otherwise direct description of colors in sRGB color space is used, both in image file formats and graphics hardware.
Pastel provides functions to create some commonly needed palettes when working with indexed images. These include a random palette, a grayscale palette, false color palettes, and the default VGA palette.
Daniel Pitts retrieved the default VGA palette from the hardware and output it into the array which is now used by Pastel.