I am uncertain about how to express an asynchronous message with the sequence diagram. In most UML I've seen, either an open arrow (stick arrow) or a half arrow is used to indicate an async message.

Create a sequence diagram by identifying objects, defining lifelines, showing message flow with arrows, using activation bars for processing times, incorporating conditions or loops, and ...

This makes both creating and reviewing the sequence diagrams easier, otherwise this detail will get lost! I have managed to change the arrow color but I could only find messageLine0 (solid lines) and ...