I know bringing 3 strong colors has been discussed, but the other 2 colors you bring are up to you. I haven’t read in-depth, so maybe this has been covered sufficiently.
Personally, for the remaining 2, I almost always bring ones that are strong against the 2 that are beside the tank.
So for a team that’s green/blue/red/yellow/purple,
I would bring 3 blue + green & purple.
I always try to bring 1 healer & 1 debuffer.
It really depends on what heroes you have available, though.
I am short on green (4/5*) heroes, so if I come across a blue tank & want to push my luck, occasionally, I will bring 3 strong against one of the flanks; or I will bring 2 green + 2 strong against a flank & 1 strong against the other flank.
I’ll try posting a video or 2 later, if needed.
As for who I attack, their team doesn’t matter, but I only attack those that offer 45+ trophies, so no worries if it takes 3 tries
Hope this helps someone!