I thought red as it is Santa's... But you could do the striped roofs you see around heritage homes, off white and maroon.

Check the scale of corrugated sheeting, convert to your scale and paint stripes that wide. Bunnings sells a wide range from what I can tell, so 25mm or wider should be ok, but perhaps roof sheeting comes larger. (I checked to see how big I needed to cut my corrugated card for my build)

Cheers
Matt.