The cones are not sensitive to a single wavelength but to a range.

The green-sensitive cones overlap with the red-sensitive cones, and to a smaller extent also with the blue-sensitive.

Full saturation red and blue are possible by emitting light on the edges of the visible spectrum.

Full saturation green, however, also activates the red and blue cones.

To cover the whole gamut is impossible, but you can approximate it with ~three green tones: a 490nm deep cyan that hits blue and green but not red, ~510nm that hits red and blue equally, and ~540nm the peak of the green cone.