Hello, you can colorize arrows.
state -direction[color]-> another_state : event
Usually I use this notation with explanation table in legend. See example:
@startuml
skinparam legend {
BackgroundColor #White
BorderColor #White
}
'Colors Definitions
!define WAY1 #Black
!define WAY2 #LightGreen
[*] -> StateA : Init
StateA -[WAY1]-> StateB : ActionA
StateB -right[WAY1]-> StateC : ActionB
StateA -[WAY2]-> StateC : ActionC
!define BGC(_color) <back:_color> </back>
legend right
| Tr. color | meaning |
|BGC(WAY1) | regular way |
|BGC(WAY2) | faster way |
endlegend
@enduml