Aloha,
So the FF on aircraft is a bug we know about, we're working on correcting this. As for regular fire, if it's secondaries and a DD meanders between you and the enemy your secondaries are shooting at, usually they will take fire, if you only hit them a couple times its not particularly a big deal. If you go pink, it means you actually dealt a substantial amount of damage to them (or sunk them).
Currently the FF feature is more to try to give players a heads up and ping them to their situational awareness. And to attempt to deter trolls that just feel the need to TK overall.
Admittedly EVERYONE sooner or later accidentally will deal damage to a team mate. I myself have gone pink (cough, during the last live stream) when I fired long range torps with a clear range and had a fast ship double back across the path of the torps and not seen them coming.
The fact that you are aware that accidents happen and at least attempt to not do so already sets you up for future success!
Mahalo,
-Hapa