It would be silly.

OK
Thanks donn.

Oh brother, donn. It is definitely NOT silly. In fact it is frequently done by professional landscapers and is gorgeous. I don't know what type of paint they use but I have seen gold and silver spray painted pampas grass for the holidays. I myself have done red with ordinary spray paint after the grass is dead. I am sure the live plumes could be painted too, especially if you just sprayed it lightly. I might try it myself, it's a great idea. See attached picture.

Niiiiiice!

Spray painting clumps the plumes together and they look stiff and plastic.

Try dipping them into or spraying them with a strong solution of fabric dye.