Abstract: A system and method is disclosed for determining the proper mixture of substances (e.g. phosphors) or sources (e.g. of light) to obtain a required or desired property, such as color or chromaticity. Steps may include mixing the substances or sources, preparing a prototype, measuring the property (such as chromaticity) of the prototype, and calculating any required adjustment in the quantities of substances or sources. This process may be repeated until the desired property is achieved, after which the mix of substances or sources may be used to manufacture products. A computer spreadsheet is also disclosed, as an exemplary embodiment, which calculates any required adjustments in the quantities of substances or sources. The spreadsheet provided is specifically configured to calculate adjustments in phosphor quantities required for manufacturing lamps for backlighting in AMLCD avionics applications.