Recently I had the outside of my home painted. The contractor wrote a good contract, but I failed to realize that some things were not in it. It reminds me of the car dealer who offered a good price on a new car but failed to mention that it did not include tires. My contractor failed to specify that lattice under a porch was included. So the painters did not paint it. To his credit, he did instruct them to paint it when I brought it to his attention. If I had the job to do over again I would look for an individual who came with referrals from happy customers rather than a franchise owner..
The companies with the best paint products are Benjamin Moore, Dunn Edwards, Sherwin Williams, and Vista Paint. As a painter I don't recommend Berh from Home Depot as much because it's quality is just marketing. Flat paint has no sheen and it shows its true color, but is not easy to wash or clean. Satin, eggshell have low sheen and is washable. Semigloss ang glossy has a high sheen and these paints are recommended for bathrooms and kitchen or where there's high humidity and steam.
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.