The Green and Gold Omni Units are used for special lighting situations.1. The Green for Fluorescent Lighting in conjunction with an FLD or 30M filter on the Camera Lens.2. The Gold for Warming Skin tones and for overall warming in flash filled available light shots.3. They are mounted the same as the regular Omni for your Flash Unit. Fits the following flashes: Canon 299 Canon 540EZ Canon 550EX Digi-Slave Dlx 3000 ProMaster FTD5700 ProMaster FTD6500M ProMaster FTD7000M Sakar 77TFZ Starblitz 3800DFH Sunpak PZ5000AF Vivitar 600N and all similar sized flashes.