How do you really know how the color on that itty bitty paint chip you're drooling over will look in real life? Will it look exactly like the paint chip? Some people say a color will look 2 shades lighter when it's painted, others say it will be darker... how do you know for sure?
Color is all about relationships. That color you are considering does not exist in a vacuum, it is part of a bigger picture that relates to your architecture, furnishings, lighting, etc. The easiest way to ensure you've got the right hue is to give it a test run.
Here's what to do, roll up your sleeves, and let's get started:
1) Paint out a 4' X 4' swatch on the lightest wall in the room - usually the wall opposite the window.
2) Make another huge swatch on the window wall itself, this is the darkest wall.
3) Don't forget the corner, where color reflects upon itself and can intensify.
Use a hot-dog roller instead of a foam brush. Why? Rolling the paint applies a more realistic mil thickness, and you'll get better coverage. Two coats are ideal (but I won't tell on you if you only manage one rolled coat for testing purposes). Nowadays you can pick up a reusable mini roller and tray for less than $10, it will raise your sampling game, and make your decision making process easier.
DESIGNER TIP #1: Review your swatches under a variety of lighting conditions; morning, noon and night.
DESIGNER TIP #2: If you are debating between more than one color, as many of us do, do NOT overlap your swatches! Remember how "seeing" color is all about it's relationship to other things? You want to see each individual swatch for it's own merits, not compared to another color.
Do you have a favorite way to test your colors? Have you ever had a paint color disaster?