An organic light emitting diode display panel includes a transparent substrate on which a matrix array of pixels is formed with each pixel including an organic light emitting diode (OLED). The OLEDS include light emitting regions sandwiched between pixel electrodes or anodes made of transparent conductive material and a common electrode made of a conductive material. The refractive index of the pixel electrodes is higher than the refractive index of the insulating layer on which the pixel electrodes are disposed so that light undergoes multiple reflections at the interface between the pixel electrodes and the insulating layer and also at the interface between the light emitting regions and the common electrode. The thickness of the pixel electrodes is chosen so that light that eventually exits the pixel electrodes after multiple reflections contains a relatively strong component of a chosen primary color.