I really don't like bright, flashing graphics. It has been proven that lights flashing at certain frequencies can actually trigger epileptic seizures. Flashing graphics can do the same. Sure, they are eye-catching, especially red ones. The red ones are the biggest culprits when it comes to bad reactions.
Bright orange is also bad.
Try to keep flashing graphics slow and try to stay away from bright reds and oranges. Yellows don't seem to have the same effect. I am not sure why. I have been told by a neurologist that I should keep flashing graphics to under sixty times per minute. Graphics that flash at a rate of sixty times per minute or greater can actually trigger seizures, especially if they are bright red or orange.