At what point in the piling up of colorless particles and forces does an actual shade of blue magically spring into existence?

I have no idea. I don't pretend to deserve a Nobel prize. But I am reasonably sure that the colorless particles and forces we need to look at to figure that out reside in the brain, not in EM radiation of a specific wavelength.

I'm also pretty sure that however the experience of seeing blue springs into existence, no magic is involved.