Frame Rate Control is a method for achieving higher color quality in low color resolution display panels such as TN+film LCD.

Most TN panels represent colors using only 6 bit

Bit

A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

s per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available from graphics cards. Instead, they use a dither

Dither

Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images...

ing method that combines adjacent pixels to simulate the desired shade.

Frame Rate Control (FRC) is a form of temporal dithering which cycles between different color shades with each new frame

Refresh rate

The refresh rate is the number of times in a second that a display hardware draws the data...

 to simulate an intermediate shade. This can create a potentially noticeable 30 Hz flicker. FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible.

This method is similar in principle to Field-sequential color system

Field-sequential color system

A field-sequential color system is a color television system in which the primary color information is transmitted in successive images, and which relies on the human vision system to fuse the successive images into a color picture. One field-sequential system was developed by Dr. Peter Goldmark...

 by CBS and other sequential color methods such as used in Digital Light Processing (DLP).

18 bit TN+film panels with dithering are sometimes advertised as having "16.2 million colors".