Is green *patina* normal on copper pipes

I was opening the access holes in my *finished basement* to vacumn up all the debris that fell while remodeling upstairsand noticed a slight tint of green around alot of the water fittings. Not the body of the copper - just around the fittings itself *elbows, etc*. Granted, this space does get cold and warm - wall cavity.

The copper in my boiler room does not show this discoloration.

Is this normal ?

That patina is a product of oxidation.

Also a product of not cleaning the pipes thoroughly after sweating the joints, which were probably fluxed with an acid flux.