The reason you would be completely colour blind is that individual cones do not distinguish colours.  The reason you perceive red light as being red is not because the L cones send a "red" signal, but because when exposed to red light, the L cones send a strong signal, the M cones send a weaker signal and the S cones send almost no signal at all.  In other words, it is the comparison between the various signals that creates the perception of colour.  When only rods are involved, we see only greyscale images, even though they are most sensitive to green light and could be thought of as M cones that are especially sensitive at low light levels.  We cannot use them to distinguish between "greenish" and "not greenish" because, like all of the retinal pigment cells including the individual cones, they only send information about brightness to the brain.  It is for that reason that you should question the "100 colours idea"; a cone monochromat would be able to distinguish about 100 separate levels of brightness, but could not tell you what colour is being displayed (indeed, they would have no idea what "colour" means).  A green monochromat would perceive a yellow light that stimulates the green cones at 50% capacity as being indistinguishable from a blue light that stimulates the green cones at 50% capacity.  Three monochromats, one red, one green and one blue, could, however, pool information and between them work out roughly what colour a trichromat would say a particular light is, just as the visual circuits in a trichromat do.