skinparam colorArrowSeparationSpace 5
|a|
|b|
start
-[#red;#blue]->
:action 1;
note right
order is red
then blue
end note
-[#red;#blue]->
|a|
:action 2;
note right
order becomes
blue then red
end note
|b|
-[#red;#blue]->
:action 3;
note right
order
restores
end note
-[#red;#blue]->
stop