A 4-bit pixel system has 16 colors in use at one time. The specific set of colors used by the system at one time is called a palette. It is often possible to change the palette, depending on the software being used.
Computer screen displays are made up of a set number of pixels, which stands for "picture elements." Each pixel system uses a set number of bits to code the color used at each pixel. The 4-bit system uses 4 bits. A higher quality system that uses 24 bits to code each color can have 16.8 million colors displayed at one time. Many computer screens used the 24-bit system.