Kelly is exactly right, the pond dye will last a long time. I only use the pond dye when spraying around the pond, and very sparingly at that. The agricultural dye is UV sensitive and will only last a few days.
I mix barely enough in to see what I have sprayed, about a 1/2 ounce in my 3 gallon backpack sprayer.
I suppose if you wanted a nice blue tint to your lawn a few ounces of pond dye would do it.
