2. Basics of Image Processing / 2.2 Picture Types
RGB images are based on the RGB color space. Each of the three components red, green and blue uses 1 or 2 Bytes per pixel. Using 8-Bit-depth, each pixel can display 256 * 256 * 256 = 16.777.216 distinct colors.
An RGB image (8 Bit) with a size of 1024 x 1024 pixels occupies 3 * 1024 * 1024 Byte - 3 MBytes - memory.