What is the sentence pattern?

Subject, verb, (object) - passive positive sentence where it is not neccessary to reference the object.

"His car" - Subject, "is painted" - passive present simple, "green"

We do not need to know who or what painted the car, just that it is green. In contrast the active sentence might read:

"John painted his car green." In the active sentence it is clear that the subject (which does the action) is "John", the verb is "paint" and the object is "car"