examples:
blue arrow on defenders : they fall back even further the moment team loses ball while giving minimal help to mid.
Pro : Good at stopping longball or/and counter plays, or when having to mark that pacy player who are stacked with stats.
con : Your mid-defense line starts stretching and thins out. You lose possession.
fix : have team on defense so it doesn't stretch in the first place.
extra : but you lose control of the field in some critical areas. DM is a good idea to fill the gap, but can't help team turning into defense mode.
Red arrow on defenders : they go foward with the ball. Your mid gets crowded.
Pro : more players in mid. easier for you to retain possession.
Tradeoff : huge space behind you.
when : if you need to overwhelm their field. short pass, challenge on whole pitch, attacking.
Fix : pacy defenders or offside trap.
extra : go for it if you are sure you can contain them.
Red arrows on AM : turns them into shadow strikers.
Pro : good at breaking offside traps or getting passes from your upfront striker
con : mid starts losing possession.
striker
red : gets upfront and challenges. Whatever you do, you are gonna do it with their defender.
pro : if you can kick a ball, it's a shooter.
con : offside traps are gonna piss you off, everything and their mom is gonna get in the way when pass comes by.
when : if you can contain your opponent and your wings are dominating. Just keep pumping the ball.
NOTE : A lot of my FM experience are mixed in. I'm sure I'm a noob in t11 than most of you guys. Take it with a grain of salt, but if the system IS based on FM, it's how the arrow works.
basically
red = this player is gonna exploit this space/player only if I get the ball.
blue = oh **** backup plan.
edit : just to clarify. every player falls back when you lose the ball, and they go forward when you retain it. There's no 'let's ignore where the ball is going cuz I'm cool like that' move. The arrow determines how you act the moment your team loses/gains the ball, not when the ball comes nearby. A winger with red will be running at their wingback the moment you gain the ball, allowing your DM/CM to try a long ball at him right after interception instead of waiting for him to get into the spot. It gives you option to time your players. Arrows can also sometimes be toxic because your Red AM could have just stuck around and distributed the ball instead of charging to their defense every time you intercept. Again, I really don't know how much of FM engine they incorporated. I'm just saying this based on FM, so take it with a pinch of salt.