Once you set your keys, you can adjust there interpolation in the Graph Editor (under Animation Editors). You can make the interpolation stepped, which will make it remain red and then flip to blue at the requested frame, or, for example, spline, where it gradually fades between blue to red. There are other options as well, but that's some examples.

As for bullet time effects, I would imagine the easiest thing to do would be to animate and render normally, then grab all your key frames and stretch them out over a much longer time frame to slow down the action.

You might also consider doing some of the slow down in post production programs, such as After FX or Premeir.