Last I checked, there was no minimal FX option for Afterburner. For the rest of the Flight set, yes, but not Afterburner.
This is particularly annoying because the FX trigger whenever the player moves while the power is toggled on. Yes, including when the character is grounded, on foot.
While I'm at it, has anyone looked at making Prestige Sprint Slide recolorable and/or minimum FX? There are some characters for whom I like the animation/pose, but the bright and unalterably pink glow is an issue.
(And way, way out there would be being able to recolor the Void Skiff - which is basically just an Energy Shield that you ride around on - or the Rocket Board, etc etc.)