I use Chartreuse colored LW helical 4" feathers which anyone can see, but I think unles your form is rock solid too many people try and "see" the arrow when they shoot it resulting in they heard lifting from anchor and them shooting high.
if you trained yourself to "not move your head" whn you shoot you'll be fine.
the one thing I think they are great for is for when you need to leave and come back and your arrow is stuck in the ground "blinking" --> perfect for the wife or kids to use when they need to call someone when a shot is made.