Methods and apparatus in which at least one first LED generates first radiation having a first spectrum, and at least one second LED generates second radiation having a second spectrum different than the first spectrum. One or more controllers control at least one of the first radiation and the second radiation so as to control at least a color temperature of visible radiation. In one example, one or more sensors monitor at least one characteristic of sample radiation and provide one or more sensor signals to the one or more controllers, which in turn control at least the color temperature of the visible radiation based at least in part on the at least one sensor signal. In various implementations, the sample radiation may be ambient illumination (e.g., natural-light and/or light from other light sources), may be the visible radiation itself (e.g., to provide feedback to the one or more controllers), or generally any desired lighting condition to simulate.