Red light is good for reading maps and navigating. It doesn't disturb night vision and can be used as signal light.
Green filters are used mostly in hunting and tactics. Green light doesn't frighten animals and its beam can't be seen from aside so it makes impossible to disclose your location.
Blue Filter Is the best for navigating and reading because you can better distinguish lines and marks in blue light. Can be used with night vision equipment.
White Diffuser for flashlights converts the focused light into a flood beam. Wider beam angle is better for close-distance applications as reading, lightening a tent and so on. The beam covers larger area and provides clear and comfortable lighting.