I used to run green food coloring, and had no probs. I didn't use WaterWetter at the time, so that's of little help.
I'd seen a post where some guy used food coloring on a different forum, and it looked to have clogged the jet tubes on his cascade. It was unclear as to which type of food coloring he used though. There is a paste type in a 1" tall jar used for cake decorating that contains solids and should NOT be used.
If you decide to try it, use the kind in the small plastic bottles that's alcohol based without solids in the bottom. Trying it out should only cost you a few ounces of WW, a quart of distilled water and some elbow grease cleaning it out if it should fail.
I really see no way of it destroying anything.
I'd think the water wetter itself is more harmfull to your system after seeing BillA's results.