Change color of background in trials?

[atfrederiksen]

Is there a way to change the background color of certain (video) trials? I'm running an experiment where the participants are Deaf signers, and I'm looking for a way that's not text to distinguish between different trial types. Specifically, I have video stimuli followed by a forced choice response, and every 4th of those trials is followed by a video recorded comprehension question. I would like the comprehension question trials to have, for example, a blue background.
Is that possible?