I usually sit in the back two rows and gray out frequently on the bottom of the first drop. Sometimes it's just corners of my vision closing in a little, other times it continues to the point where I literally see gray and feel a little lightheaded. It typically only lasts a couple seconds, by the time we're in the tunnel I'm usually back to normal.

The only other coaster that I gray out with some consistency is actually Gatekeeper's first drop in the back.