Hello can anyone explain how arrows work?

I have been reading around and have come up with two completely different scenarios:
a) Red arrows affect team only when attacking, blue only when defending... so that your team reshapes according to the arrows.
eg on 442:
-A-A-
-----
LC-CR
-----
LD-DR
--G--

When attacking translates in:
-A-A-
L---R
-C-C-
-----
LD-DR
--G--

And when defending becomes
-A-A-
-----
L---R
-C-C-
LD-DR
--G--
b) arrows just affect the formation in other ways, having people attack more so unbalancing their role regardless of defending or attacking.
EG still on 442 above:
-A-A-
L---R
-----
-C-C-
LD-DR
--G--

so my question: what is the effect of arrows if you know?
Thanks in advance