The lookup table color filter allows you to define the mapping of input to output pixel values for each color: red, green, and blue. This filter is similar to the standard lookup table with the exception that you can add or reduce emphasis by each individual color.
The lookup table uses a segmented line with three adjustment points you can drag to adjust the input to output pixel mapping for each color (red, green, and blue). Tabs at the top let you select the color affected.
The bottom axis represents input values while the left axis represents output values. A value of 0 is 100% red, green, or blue while a value of 255 is 100% white.