It depends on your "bullet-time" model whether it's red-shifted or not. Much "bullet-time" is explicitly just a special effect, i.e., the idea is that the action is still occurring in real time but we're having it slowed down so we can see it, understand it, and enjoy it. In that case we are simply shooting the scene with a high-FPS camera. "Technically" we should indeed get a dimmer scene, just as real high-speed cameras do, but it's not
that unrealistic that it's compensated for, again, just as in real life when the Mythbusters go to a high-speed camera shot they've already compensated for that.
If you have a "real" time slow-down, exactly what happens depends on your model, especially where the photons cross whereever the effect is occurring. It is true that one model could be that a photon crossing into the effect keeps the same "real" Hertz, in which case you'd see it red-shifted. However, since in the end the entire idea of such sharply-localized time variance without a corresponding gravity field is complete nonsense, the truth is that no matter how you slice it the result is gibberish, so it's just as sensible to let the field "keep" the old photon's frequency too.
However, I'd point out that "real" time slowing in the movies is fairly unusual. Mostly it's the first kind. There's a number of sci-fi books with a variety of "real" time slowing effects, though.