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.
Remember: You want to get the highest quality paint your budget will allow to ensure its lasting beauty. You'll also need painting supplies like primer, brushes, rollers and painter's tape. A professional will have these items on-hand. According to statistics, paint and other supplies account for about 15 percent of a professional painter's total cost; labor will factor into 85 percent of their charges.
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.