I would bet the green is from the oxidation on that valve/pipe being flushed down by the leak

Peel off the tape to see where the leak is coming from. It may just be a pinhole, maybe it's a crack. If the leak is coming from high enough on the pipe then your simplest bet will be cut the tube and use a sharkbite fitting to replace the valve. They sell shark bites that already have the valve on it. Just remember to shut the water off to the house before you cut that line. If you aren't comfortable doing repairs then get a professional.

For removing the stuff off the floor you can try CLR or even vinegar.