Illumination of the skin by substantial, monochromatic light emitted by LEDs, produces positive therapeutic effects for the treatment of a wide variety of skin conditions. Arrays of LEDs comprising multiple emission colors are preferred light sources for these applications, however, achieving uniform and efficient illumination of a skin target area in close proximity is difficult due to the point-like emission and narrow divergence of lensed LEDs. An illumination apparatus and method, provides a LED system that produces uniform and efficient illumination by combining a well-distributed computed arrangement of each of the LED colors on the array, to enhance the spatial overlap of individual LED outputs across the target area with a diffuse secondary reflector between the LEDs having high reflectivity to further enhance illumination uniformity by allowing light to bounce between LED array panels and the skin.