100x is sensationalist phrasing. ~7 more bits of color resolution better way to think about it.
You can't replicate RGB with just R an B, even if you crank up the resolution.
Assuming that the cones of different frequency range have approximately the same degree of sensitivity, I'd be thinking that the number is about n^(4/3) where n is the number of colours perceivable by trichromats.
But even if that's true - which I doubt - the additional colours are in unlikely to have a useful distribution, and will be centered around the frequency response curve of the fourth cone (I believe it's generally in the yellow spectrum; somewhere between red and green).