Red: Used in tropical water in depth of 30-65feet / 10-20 metres, at noon ( when the sun is high in the sky).
Yellow: Used in tropical waters, in the morning or shallow water of up to 30 feet / 10 meters.
Purple: Used in green water, fresh water such as lakes and streams or dusk hours.
Grey: great for removing unwanted reflections from non-metallic surfaces, such as glass or water. Mounted on a rotating frame, this filter can be adjusted to block different levels of reflection.
Orange:Used in water in depth 6~17,By restoring the red which is absorbed by water