i painted a room from flat white to royal purple. The areas i put primer up took 2 coats. the rest of the room took 1. Used Benjamin moore regal eggshell. it looks pretty good. will say painting over the flat white used a TON of paint, so in the end it may have been a lot cheaper to do 2 coats + primer. I used 4 gallons for a 14x10 room including ceiling, 90% roller, 10% brush.