The vast majority of color blind people are in fact what are known as anomalous trichromats. They still have three photoreceptors, but the ‘green’ receptor is shifted a bit towards red. The effect is subtle: Certain reds might look like they were green, and certain greens might look like they were red.
Thus the question: Was it possible to convert all reds to a one true red, and all greens to a one true green?
The answer: Yes, given an appropriate colorspace.