Green light has a very narrow band. For that reason, it is often used for night hunting. Animals are not frightened by green light, and it cannot be seen from the side – only straight on. This makes it the ideal filter for your tactical flashlight when stealth is at a premium.
Some lights, like the Nitecore CG6 feature a secondary Green LED while options like the MH25 can have an easy to use filter you can carry. With the human eye being most sensitive to the green range of light this makes it an optimal color to use when traversing through the forest when you are using a low intensity.
Blue filters are often used when reading maps or other writing because they cast black lines in stark relief against white paper. If you are on an overnight hike or mission, a blue filter will certainly help to keep you on the right path.
One of the additional uses of blue filters is for hunters. Tracking wounded animals at night means picking up a blood trail. The blue light helps the blood stand out against foliage.
So if you want a full package hunting experience, both lights would be necessary!