Is red the most popular? I remember when my daughter flew over Poland on her way to Warsaw, she said all she saw was the red roofs of buildings.
And...are those red roofs actually made of real tile?
Historical buildings always have real tile, even after renovation.
As for private houses, it is mixed due to costs - about one quarter use ceramic tiles while the others prefer different sorts of cheaper steel tiling. Red colour is the most popular. Rarest - blue and green. Even black can be seen from time to time.