It takes more than a year for a pond to truly mature, Im not suggesting you wait that long. In fact, Im not just suggesting you do nothing, other than accepting your pond is brand new and not taking desperate measures like emptying it.
I believe you bought an extra UV by now? lets see what that does. But green water, within reason (*) is nothing to panic about. If anything, its the opposite, your koi will actually love it. Its just us humans who dont like not seeing them. If you have enough filtration and enough plants, it will usually just go away after a few weeks. The things that you need to worry about more at this point, is PH, ammonia and nitrite.
* Only if the green soup becomes really thick, it might become a problem as massive amounts of decaying algae can poison the water and deprive it of oxygen. If you are worried about that, add an airpump and do partial waterchanges.