Painting Horn Plates

Hi All

This is a "google" Oh! sorry question?

What is the convention for painting the Horn and Spec plates. I see the inside around the motion area is usually red (got a red to do this) but the question is.

How far up the side should the black be ie is it just where the plates would "touch" the boiler or is it higher?

Is the outer faces of the spec plates done in engine colour or in the red?

Are the inner surfaces of the horn plates out with the spec plates done in red or engine colour?

Hope this makes some sense.