Hi,
Actually, "Database" has its own skinparams and does not share setting from "Package" one.
So you should use something like:
@startuml
skinparam database {
border {
color grey
thickness 1
}
BackgroundColor yellow
Font {
Color LightGrey
Size 14
}
}
package "<size:18>styled</size>\nshould be styled" <<Database>> {
}
package "<size:18>styled2</size>\nshould be styled" <<Database>> {
class foo
}
@enduml
Does it make sense for you ?