If "All" wavelengths are shown, then the plot is referenced to the primary wavelength based reference sphere and chief ray. The resulting OPD values, however, are in terms of waves of each respective wavelength. If monochromatic, then the reference sphere and chief ray for the selected wavelength is used as a reference. For this reason, the data for non-primary wavelengths could change when switching between monochromatic and polychromatic displays.