Greenish Deposit on Outside of Copper Pipe in Bathroom
That normally means there was a water leak at some point.  If you look at the pipe on the left in your picture, you can see a small trail coming down from up above.  Is there any sign of water above the floor/cabinet?  A small amount of green on copper usually isn't anything to worry about.  You just want to make sure that whatever is leaking has stopped.

If there is still a leak, clearly you'll need to fix that.