CTB (Colour Temperature Blue)
CTB filters are designed to increase the colour temperature (measured in degrees Kelvin) of your flash. Use a CTB filter to match your flash output to cool daylight lighting environments.
CTO (Colour Temperature Orange)
CTO Filters are designed to reduce the colour temperature of your flash. Use a CTO filter to match your flash output to tungsten lights, or simply to give a pleasing warm tone to your portraits.
+Green
Plus Green Filters are designed to be added to a flash being used as a fill light where there is a predominance of fluorescent lights that cannot be eliminated (fluorescent light sources have a very high green peak).