I hear that kudzu makes purple honey. Back when we had a bee inspector, he said he once saw blue pollen in a hive and asked the beekeeper where he thought it was coming from. The farmer said, you won't believe it unless you see it and took him to a barn nearby where the bees were collecting the paint off of an old tractor...
Blue pollen is not something unussual. If you zoom my first picture you can see the blue pollen on the bee foot. Also, the pollen of this flower is blue.
About blue honey, I think is from grapes or berries.
In my area, when we have drought in the fall is very common to see bees on grapes, but only after a hornet cut it first.
Also, on drought, the concetration of sugar in grapes is very big and very appealing for bees.
All the best.