Dang, I was hoping you would get an elegant solution in the comments.
I just checked AI for pond dyes for potable water, and it could find zero for retail sale.
Time to switch to Plan B?
Is there a place on your property where you would like a small, decorative pond? If so, I would calculate your "summer" water usage, and build a supplemental pond with that volume. (If that calculated pond is too big for some reason, do a pond with half the volume, and plan for one re-fill during the algae season.)
Fill the pond with water and then perform your cutrine and dye treatments in the main pond.
You could then fill your potable pond with an aggressive spreading water lily. They will shade out the algae in the potable pond. They should be tough enough to survive as you draw down the level of that pond. Extensive pad coverage will certainly reduce evaporative water losses from your potable pond. However, I don't know if the plant transpiration losses would be less than or greater than your projected evaporative losses without the lily pads?
Maybe add a fountain and some decorative shallow emergent plant (like from the iris family) so the potable pond is attractive from the view from the house.
Remember that "the dose makes the poison". If you need to draw some more potable water from your main pond, it would certainly be safer to do it 90 days after treatments, rather than starting on the day after treatment. (Still don't know if it would be absolutely safe?)
Good luck in your future battles with algae! It is a very common problem for pond owners. You might read some of the old algae threads, since there are other partial solutions besides chemical treatments.
