Bear in mind I'm referring to the philosophy that was used in the '55 model year, but from what I have seen, that practice carried on through the years Ford offered two-tone paint jobs.
Regardless of whether you had a styletone or a unique two-tone pattern (yes they were different), the door posts, door jamb and exposed areas of the door shell on the sedan models were painted whatever the base color of the car was.
Lets take two cars, both are blue-white two-tone:
A styletone blue-white car had blue below side trim, white above side trim ending at top of rain gutter, then blue on top. the base color used to paint the entire shell of the car was white; (firewall, undercarriage, floor, inside doors and doorjambs).
A unique two-tone blue-white car could have blue below side trim, white from above side trim to the belt moulding, blue from above side moulding to top of rain gutter, then white on top. However with the unique two-tone, the base color used to paint the entire shell of the car was blue.
Thus, you can see the posts were always the base color, inside and out.
Below the trim line where the two colors meet at the inside of the doors, which are the base color, the secondary color ended at the factory seams (the little lip of metal that is folded over all around the door inner shell).
The unique two-tone pattern was only available on Fairlane series cars all of which had stainless trim on the rain gutter, further accentuating the transition of colors at the top.
BTW, sometimes the unique two-tone cars had the color scheme reversed such that the white was on bottom, blue from top of side trim to belt moulding, white door posts, then blue on top again. In that case the base color was white.
Blows your mind doesn't it?