Lawrence, I ended up looking at the relation between E8, Jordan algebras of 3x3 matrices of octonions, triality (which for the 3x3 Jordan algebra defined matrices amounts to a shuffling of the matrix elements), the 3x3 circulant primitive idempotent complex matrices, and the Koide mass formulas yet again. It is a little too much for me to chew, but there are a couple of papers that gave an idea of what is going on and what it has to do with string theory. The papers I ran into were these:
The exceptional Jordan algebra and the matrix string
Lee Smolin
http://arxiv.org/abs/hep-th/0104050
The Geometry of Jordan Matrix Models
Michael Rios, 2005
http://arxiv.org/abs/math-ph/0503015
I ended up looking at this from reading the Wikipedia article on Heisenberg's matrix mechanics. The Koide formula is related to what Heisenberg did in that the circulant 3x3 matrices are the density matrix version of three basis states [i.e. the three states (1,w,ww)/sqrt(3) where w is a cube root of unity] for a 3-d Hilbert space that happens to be MUB with respect to the usual diagonal (1,0,0), (0,1,0), (0,0,1) basis. And the Fourier transform is equivalent to diagonalizing a 3x3 circulant matrix as Kea pointed out:
http://kea-monad.blogspot.com/2007/10/m-theory-lesson-108.html
Anyway, the circulant matrices used in Koide's mass formula turn out to be of the form one would get if one put O_0 = O_1 = O_2 in the 3x3 matrices of octonions in either of the above papers. The triality defined on equation (7) of the Smolin paper turns out, when applied to the Koide density matrices, to be an identity. [It basically cycles the _0 to _1 to _2 and since these are equal, it leaves these matrices unchanged.]
When that triality is applied to the other density matrix basis set for 3-d Hilbert space mentioned above, that is, the diagonal primitive idempotents: (1,0,0), (0,1,0), (0,0,1), the action is to cyclically commute these three elements.
But a 3-d Hilbert space MUB contains 4 basis sets. It turns out that the action of Smolin's triality on the third and fourth basis sets also permutes the elements while preserving the basis set [that is, the action is like the action on the diagonal primitive idempotents]. The 3-d Hilbert MUBs are listed (in state vector form) near the bottom of this blog page:
http://carlbrannen.wordpress.com/2008/02/06/qutrit-mutually-unbiased-bases-mubs/
So as far as this goes, it seems to me that the natural assignment for the triality operator mentioned in Smolin's paper, in the context of the Koide mass formulas, is that it changes color charge R -> G -> B -> R. [And so I don't think this is the triality that changes generation number.]