Exterior liberties

Who says you have to follow the rules? Take this fabulous example in Dresden, East Germany.
image source
In addition to the most fantastic drain pipes I have ever seen in my life (!),
notice the wavy gradations of blues and greens running across the facade of this building.

Why do drainpipes have to run straight down the side of a building? And why do facades have to be only 1 or 2 colors? Who says?