Guesstimating roof types and colours

[pantomico]

Here in Denmark, we will be mass-importing data from the government. We know roof-material, but not colour or shape.
However, roofs with tiles or eternit will never be flat. And 99,9% of buildings with tarpaper or eternit on the roof have dark grey colour. I think it is wrong to add these colours to the database without being sure, but as a renderer you have more freedom. You are just supposed to make a guess.
So I propose:
roofmaterial = tiles -> roof is gabled unless specified otherwise
roofmaterial = tarpaper -> roof is dark grey unless specified otherwise
roofmaterial = eternit -> roof is gabled and dark grey unless specified otherwise

One could imagine something similar for building material.

[pantomico]

For testing and demo, you can look at Rødby in Denmark, also the holliday homes to the east of rødby.