If you're going to do any part of the painting or prep work on your own, you must know that the first step in preparing a surface is washing it. Since dirt can affect the smoothness of a surface area -- and therefore paint's adhesion to it -- use soap to remove any dirt or stains. Make sure there's no soap left on the walls when you're finished; also make sure to remove any gloss with sandpaper and vacuum up the leftover dust.
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.
Picking exterior house paint colors is a lot different than picking a color for a shirt or a car. It may help to drive around to observe colors that other homeowners have combined on homes that are of similar size and design as yours. There are also online resources that provide homeowners with the ability to create virtual makeovers of their home by combining colors together through their software programs as well.
So sad that Angie's List requires the contractor be notified!! They have lost me as a client. If I'm dissatisfied and want to give an "F" rating (question/workers...I SHOULD NOT be intimidated into passing up an opportunity to explain my experience! There is NO WAY my contractor got an Aplus rating from over five hundred people....so someone was lying....yet I can't report that without the contractor knowing it? REALLY?
I used to work at Sherwin Williams. The best thing to do is specify that you will purchase your own paint. If the painter objects strenuously, he was plaanning on making money in the ways this article outlines. You might pay a few dollars more for paint, but you will have control of the quality of what goes on your walls. Never skimp on paint quality.