The term "dichroic" applies to GE MR16 lamps specifically, not in general to low-voltage halogen lighting. For the GE MR16 lamp, dichroic describes the type of coating on the reflectors. These coatings can also be described as "multi-layer interference films". They are made up of dozens of layers of thin materials that have the unusual property of selectively reflecting or transmitting certain wavelengths of visible light, IR, and UV. Such dichroic coatings have been used since the 1960s to reduce the heat in the beam of certain reflector lamps (GE calls them "Cool-Beam" lamps). MR16 ConstantColorâ„¢ coatings are more sophisticated since they not only reduce the heat in the projected beam (up to 66%), but also absorb UV and control the color and amount of the light from both the front and back of the lamp - keeping it constant over the life of the lamp. The coatings are also very durable and will not flake off or deteriorate as the lamp burns. *from www.gelighting