In the current, reworked page editor, place holders are always colored gray. They should, however, also be colored in the very light green if the area they are contained in, is colored in the same green already.

The very light green acts as a halo for the current selected item and helps understand the context it is placed in. If e.g. we've selected a component, its bar is dark green, all its siblings and its parent area are colored in the very light green of the halo. This also applies to placeholders.