KNOW YOUR LIGHT SOURCE!
When you paint know your light source or type of light that you will use for the room, or if choosing exterior paints, take the sample outside and look at it.
The above picture is from this months BHG mag. Love there paint sample page. This months was picked for me. Those are my kind of colors, no grays of various shades of gray, rich color is what I like.
Now the two pic are obviously of the same page, however the one on the left is taken in direct sunlight and the right side is taken with fluorescent overhead lights, which is what you will find when you are in the store choosing colors, so take those chips and if they offer it usually there is a small light box that has 3 types of light colors that you can switch between. USE IT. However an even better choice, buy a sample of the color or colors you want and take them home and paint a patch.
When we painted our former house prior to selling it, I would go outside Home Depot with the little swatches and see if I liked the color in sunlight, I bought about 6 different colors and the back of my house had 3x2 sections painted in the different colors. I looked at them if full sun, cloudy and dusk to see if they still worked. You would be amazed at the changes that occur. Now indoors you still want to look at it with the light source that will be used in the room but also, like a bedroom what does it look like with just a lamp on, is the color still what you want. Color creates emotion, color heightens emotions. Think of the use of the room when choosing your color and also maybe the lighting needs to be changed, change the lights first so you have your light source.
Back to the two pics at the upper left hand side is color called Lion's Mane from Olympic. In natural light it is much more toffee than yellow, in fluorescent lighting it's more yellow. The Cachet Cream by Sherwin Williams, is a pale creamy caramel in natural lighting. In fluorescent, it's off white.
Lighting can completely and totally change the color of the color you have fallen in love with and the mood you want. Seriously who has not fell in love with a color swatch and carried it around in your purse, just to look at it?