So, so... our color system is, pardon my maths, some kind of simplified Fourier encoding of the frequencies (real) into a finite number of fixed frequency component ?
It's just a 3-d subspace of the continuous (infinite dimensional) input space. If you start in the em frequency domain (which is the only sensible thing to do) nothing is cyclic, so it is not customary to call them Fourier coefficients - but I think you got the concept.