A color tunable light source comprising: a first LED arrangement operable to emit light of a first color and a second LED arrangement operable to emit light of a second color, the LED arrangements being configured such that their combined light comprises the output of the source and control means operable to control the color of light emitted by the source by controlling the relative light outputs of the two LED arrangements wherein the control means is operable to dynamically switch the outputs of the LED arrangements and the color is tunable by controlling a duty cycle of the drive current. One or both LED arrangements can comprise at least one phosphor and an associated LED that is operable to irradiate the phosphor with excitation radiation of a first wavelength range such that the phosphor emits light of a different wavelength range.
