When To Use BLUE ARROWS on central DCs

I never used the blue arrows until the very end of last season (Level2).
This season I have used the blue on all the DC ( 2 or 3 players, depending) and have used the red on the DR/DL players.
The DMC, if used, does not use red only blue or no arrow.

I have found that I am not conceding many goals this season.
Are my DC players sitting too far back this season and letting the other players score, while they protect the goal?

What is you defense style / tactics like?