Shadows are entirely different from silhouettes. It isn’t just herons that are grey, so are battleships and all naval vessels. It is entirely a matter of personal choice but I ahve painted the top kits that I use for fishing up in the water. It certainly doesn’t do any harm apart from the oddd sarcastic comment on the bank but if it helps to put one more fish in the net then it is worth it.
The weight aspect is just a joke! compare a thin coating of paint compared to an ordinary elastic. Yet alone hydro! You notice absolutely no difference with a painted top compared to a standard one.