Hello Fabio Manniti,
Yes, it is called Master - you can then create the common layout sections (e.g. header, sidebar).
The layout can be choosen when creating a new Master entity:
Then all you need to remember is to go to you mashup and set the Master in the Mashup properties.
From the perspective of styles, background colors and so - no, there is no OOTB possibility to configure that since StyleDefinition parameters are not boundable in widgets.
Hope it helps.