Complex sentence: The hall was originally supposed to have been plastered and painted blue, a colour scheme that would have resembled the water of the bay, but the architect Ragnar Östberg changed his mind during the building of the hall after he saw the red brick.
Split into simpler sentences: The hall was originally supposed to have been plastered and painted blue, a colour scheme that would have resembled the water of the bay. But the architect, Ragnar Östberg, changed his mind during the construction of the hall after he saw the red brick.