Color Level options for Spectrum Plots are enabled in Color on Density Display Mode only.
Color Levels for Spectrum Plots can be formatted in the same manner as for 2D-Density Plot Color Levels. Below is an example of a plot with customized color levels (Figure 8.93). Please also see the Formatting a Spectrum Plot chapter for additional details and examples.
Figure 8.93 - The two Spectrum Plots in the center of the picture have customized Color Levels.