As in all things manufactured, cost is key. If you add a dye to a
pesticide, no matter how benign, the EPA would put you through
such a wringer to prove it is non-toxic, probably a million or so
at a minimum, that the return is not worth the investment.
Just the chemical aspects of it are interesting. You would have
to show what is the dyes interaction with honey, the breakdown
products and what they do to wax, honey and bees. All the things
you have to do with the pesticide by itself. And most dyes used
in food do not break down because the manufacturer wants them to
stay colorful. That is the intent of adding the dye. And what
about the breakdown time? Enough to be all gone before the bee
picks some up and it becomes stable in the honey. And you end up
with purple honey. Or pink bees. Would be unusual.
Bill T
Bath, ME