Today, I installed the exterior window trim. There are two main approaches to this, based on personal preference. One option is to leave the white edges of the dollhouse wall visible between the interior and exterior trims, as shown in the dollhouse box photo. I usually prefer this method because it makes the windows stand out. The other option is to paint the edges of the wall to match the window trim. For this dollhouse, I chose to paint the window edges to match the trim. I felt that leaving them the same color as the walls created an unappealing "striped" effect. With so much half-timber trim on this dollhouse, the white edges would have resulted in a distracting pattern of white and dark brown stripes from every angle.
It's best to paint the wall edges after installing the exterior trim but before adding the interior trim. Keep in mind that you'll need to install your window panes first for the interior windows, which makes it difficult to paint those edges later.
Below are pictures of both examples - one showing white edges between the window trim and another with edges painted to match.
