Britguy - the stocked fish attack green & green/red strike indicators quite a bit. i have had them grab it so hard they end up getting snagged because they release my float so the hook comes to it. A guy at my local lake has gone as far as tying a dry fly in the colours of strike indicators and on some days he can slay pretty good with it but not very often. Im not sure if they think it is powerbait or not however they do seem to strike it fairly hard most of the time so i would think they think its something tasty

I have also had a couple fish take the indicator and not want to let it go

almost had one to shore one day it finally let go when i was reaching for it, i almost got hooked in the face when it let go as the hook was still 4 feet below the indicator LOL
I have stopped trying to figure out these stocked fish, there is just no steadt rhyme or reason to them. I have found a few things that work a majority of the time and just stick to those

You know one of them flies i speak of