This is a color model display format that uses the three primary colors (blue, red and green) to create an image. Each color can have up to 255 gradations, allowing for color depths of up to 48 bits. RGB supports the display of 16,777,216 colors.
ICO is a file of this format usually contains a small image icons of different resolutions (16x16, 32x32, 64x64 pixels) and various color depths (16 colors, 32, 64, 128, 256, 16-bit, and so on). Used to display files and folders in the graphical user interface (GUI) operating systems. This format can be opened with the help of the program ACDSee.