Oblique Illumination Dispersion Staining
Transmitted Oblique Brightfield Illumination, 20X Objective

These are the colors seen when using oblique illumination with the 1.67 optical glass standard in Cargille Melt
Mount 1.662 refractive index liquid. The wavelength at which this glass and this liquid match is 490 nanometers.
The difference in dispersion is 0.011.