This uses "as" and works.

@startwbs
<style>
.foo {
LineColor #00FF00;
}
.customer {
BackgroundColor orangered;
}
</style>
* Test
** A topic
***[#blue] "common" as c1
***[#blue] "common2" as c2
** "Another topic" as t2
t2 -> c1 <<foo>>
t2 ..> c2 #blue
@endwbs