Depends on lots of factors - your light fixtures, your natural light and reflectivity of items in the room. That's why you make sample boards and move them around the room and check them under different light conditions - like raining, sunny, table lamps only, ambient ceiling fixtures only, all lights on, tv on. You can see it will take a bit of thought and time. Make the boards nice and big.

Good question, but once dry the color should be close to the color chip. The great thing about doing boards is that you can move them around the room. Look at the colors at differnent times of day. Another thing is that you can take them shopping for accessoiries.