As you walk through your lighted rooms (preferably day light) see if the new coat has light spots showing the precious paint. This is call "bleeding through". This means that there's only one coat of paint or the paint was diluted or the trasition of colors were from light to dark (or the other way around) and primer was not use or the painter is inexperienced.
A painting and decorating contractor prepares by scraping, sandblasting or other means and applies any of the following: paints, papers, textures, fabrics, pigments, oils, turpentines, japans, driers, thinners, varnishes, shellacs, stains, fillers, waxes, adhesives, water and any other vehicles, mediums and materials which adhere by evaporation and may be mixed, used and applied to the surfaces of structures and the appurtenances thereto for purposes of decorating, protecting, fireproofing and waterproofing.
When hiring a contractor it is always best to hire one who is personally referred to you by someone you trust. Hiring through ads or phone book is hit and miss. Check with your local paints stores, they know the good guys from the bottom feeders. Go to the stores that sell the high quality paints like Benjamin Moore(nonpareil), Pittsburg, Sherwin Williams or Glidden. Don't go the the big box stores for referrals, the people there don't know squat!
When I had my interior painting done, after clearing out all of the furniture, myself, I also removed all of the wall plates in all the rooms to be painted. They were a beige color and probably yellowed. The wall was originally an off white and I had it painted a light-mid grey, so those wall plates would look terrible. After pricing replacement plates, switches and outlets (Would have been way too expensive to replace all of them), I decided to just paint all of the wall plates, switches and outlets (Used just a black gloss spray paint). I sprayed the plates outside and used a small brush on the switches and outlets. It worked out just fine and the blacks plates, etc compliment the wall color. It has been 7 years and the plates, switches, outlets are holding up well.
The Lead Renovation, Repair and Painting (RRP) Rule establishes requirements for firms and individuals performing renovations, and affects contractors, property managers, and others who disturb painted surfaces. It applies to work in houses, apartments, and child-occupied facilities (such as schools and day-care centers) built before 1978. It includes pre-renovation education requirements as well as training, firm certification, and work practice requirements.