The best time to tackle windows is in the beginning of the day, when you're fresh," says Doherty. "But it still takes me an hour to do a standard window." For double-hungs, begin by raising the inner sash and lowering the outer sash until their positions are almost reversed. Paint the lower half of the outer sash first, then the entire inner sash. Once the lower sash is dry, return both to their normal position, but leave them slightly open. Finish painting the outer sash. "Windows take too long to tape," says Doherty. When painting, overlap the glass by 1/16 inch to seal the wood.
I agree with JHs. If there is no new color on it at all, just talk to the painter about it, if it was an honest mistake (which can happen very easily while painting) your painter should have no problem fixing it. However, in my years of experience, it is not unusual for 2 coats of door paint (good quality) not to cover very well at all. I once painted a red door 7 times, plus a tinted prime coat before I found the door to be a solid color.