A tutorial that demonstrates this shader can be found here.

 

Sampling

Channel 

Position Offset

Interpolation

 

Color Correction

Similarly, Volume Sample RGB has a set of parameters to alter the output color regrouped in the Color Correction tab. The operations are applied in the same order as the parameters.

Gamma

Hue Shift

Saturation

Contrast

Contrast Pivot

Exposure

Multiply

Add