Is it just unsighly when copper pipes turn green on the outside, or do they degrade to any significant level?
Clean them right away!!
The installer hasn't wiped off their flux after sweating up, and it will eat through your pipes.
The green is copper oxide, and a sign of corrosion. Get some steel wool and clean it off

The green is copper oxide, and a sign of corrosion. Get some steel wool and clean it off
Nope, copper (1) oxide is brick red, copper (2) oxide is black. Copper carbonate is green.
http://en.wikipedia.org/wiki/Verdigris

http://en.wikipedia.org/wiki/Verdigris
Have Wiki got an entry for copper pipes and fittings painted gloss white 3 times a year for 20 years and why?
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