You can try the last beta: https://dl.dropboxusercontent.com/u/13064071/plantuml.jar
With this beta, you can have:
@startuml
skinparam ArrowColor<<read>> #green
skinparam ArrowColor<<write>> #line.dashed:blue;text:coral
component node1
component node2
component node3
node1 --> node2 <<read>> : link1
node1 --> node3 <<write>> : link2
node2 --> node3 #coral;text:red : link3
@enduml
skinparam componentArrowColor is also valid, but the recommended is skinparam ArrowColor.
Remember you can also set the style individually:
New syntax:
node1 -> node2 #blue;text:red
Old syntax, not recommended:
node1 -[#blue;text:red]> node2