Illumination systems are disclosed, which include illumination channels of different colors and at hast one image-forming device. Each illumination channel, in turn, includes a bank of light sources, and the image-forming device is disposed to receive illumination from at least one of the illumination channels. At least one of the illumination channels includes an optical element, such as an optical element having optical power or a homogenizing optical element, that is not shared with any other illumination channel and is preferentially constructed or preferentially positioned for the color of its illumination channel.