Gray Scale or Desaturate radio buttons.
You can only select one. Grayscale does a luma-preserving total de-saturation of the Input Shader (which can, of course, be more complex than the Texture map illustrated)
Desaturate activates the sliders in the box, allowing finer control over the color saturations.
Master Saturation Modifier.
Moves saturation of all colors simultaneously. Acts in tandem with the color Saturation Modifers. Positive numbers increase the saturation, negatives decrease it.
Red, Green, or Blue Saturation Modifier.
Moves the saturation of each color independently. Positive numbers increase the saturation, negatives decrease it. Acts in tandem with the Master slider.