The arrows are like 'mentality' for the players

No arrows is a balanced mentality, player will push forwards or cover back like you would expect for their position - e.g. full backs join attack sometimes, but mainly defensive

Blue arrow is defensive mentality, player will focus on dropping back to cover and rarely join attacks - e.g. full back with blue arrow will act as a defensive sweeper

Red arrow is attacking mentality, player will focus on getting forward leaving defensive work to others - e.g. Full back acts more like a wing back, going forward often


Some people use this to force specific instructions, e.g. red arrow on striker makes him stay near the goal, blue on defender makes a sweeper

I have two teams, one (token buying) plays 4-4-2 classic with no arrows, one plays approximately a 5-3-2 with DMR/L and AMC who have red arrows. AMC scores and assists a lot!