Optical stacks configured to reduce variation of color with view angle in organic light emitting diode (OLED) displays having an emissive OLED layer are described. An optical stack having first and second layers with differing refractive indices includes a nanostructured interface between the first and second layers. The second layer can be disposed between the first layer and the emissive layer with the nanostructured interface proximate to, and outside of, an evanescent zone of the emissive layer. The nanostructured interface has a substantially azimuthally symmetric power spectral density (PSD) and a wavenumber-PSD product has a maximum for a wavenumber larger than 6 radians/micrometer times the refractive index of the second layer. For all wavenumbers lower than 6 radians/micrometer times the second refractive index, the wavenumber-PSD product is no more than 0.3 times the maximum.