Hello K,
Here is an attempt, using style:
@startuml
<style>
timingDiagram {
LineColor transparent
timeline {
LineColor #3
}
clock {
LineColor darkgreen
}
concise {
LineColor darkgreen
}
robust {
LineColor darkgreen
}
binary {
LineColor darkgreen
}
}
</style>
clock "Clock_0" as C0 with period 50
binary "Binary" as B
concise "Concise" as C
robust "Robust" as R
@0
C is Idle
R is Idle
@100
B is high
C is Waiting
R is Processing
@300
R is Waiting
@enduml
Awaiting style for the time axis... (as a wanted request to PlantUML team... 
)
If that can help,
Regard.
