I'm not sure about shifting wavelengths (that seems way too complicated), but you could just block all out the red light on the right eye and all the green light on the left eye, and that would do the trick for someone who's red/green blind.
Instead of putting these two filters on different eyes, you could put them one after another in time, I guess.
Or you could put a green-blocking filter on the left side of your view (on both eyes) and a red-blocking filter on the right side of your view (on both eyes), and you would move your head around a bit to figure out green from red.
Or you could have a checker-port pattern with the two filters or so.