A system provides white light having a selectable spectral characteristic (e.g. a selectable color temperature, delta uv, and intensity) using a combination of sources (e.g. LEDs) emitting light of three, four, five, or six different characteristics, for example, one or more white LEDs, and one or more LEDs of each of three primary colors, plus cyan and royal blue. A controller maintains a desired spectral characteristic, e.g. for white light at a selected point on or within a desired range of the black body curve. In addition, the controller provides selectable adjustments for values of the spectral characteristics, while maintaining substantially constant overall output intensity for the light output of White LEDs, thereby achieving Maximum Utilization.