The invention provides a method of forming a patterned phosphor structure having red, green and blue sub-pixel elements for an AC electroluminescent display. The method involves selecting first and second phosphors, each emitting light in different ranges of the visible spectrum, but whose combined emission spectra contains red, green and blue light; depositing and patterning the phosphors in a layer to form a plurality of repeating phosphor deposits; and providing means associated with the phosphor deposits, and which together with the phosphor deposits form the red, green and blue sub-pixel phosphor elements, for setting and equalizing the threshold voltages, and for setting the relative luminosities of the red, green and blue sub-pixel phosphor elements so that they bear set ratios to one another at each modulation voltage used to generate the desired luminosities for red, green and blue; and optionally annealing the patterned phosphor structure so formed.