Ok, i'm working with the "enhancer" moment right now.
It's gonna be a liquid, that Quiet will use on Brutus cock/balls, to give him more strength/power.

What do you think of color? I also have an idea, when she will pour some liquid on Interrogator's asshole, before the actual penetration, to threat her even more (and so the cock will grow even bigger, after the penetration). So it should be good visible on Interrogator body as well.

Here's the examples:

Blue
Black
Green
Purple

VOTING LINK HERE