You'll often hear discussions about the relative temperature of a color, whether it's cool or warm. The color wheel tells you which.
Half of the color wheel--from red to yellow-green--is considered warm. These colors appear as if they are advancing toward you, appearing nearer. They can help create a warm, cozy atmosphere.
The other half--from green to red-violet--is considered cool. These colors appear to recede, as though the space is expanding.
Green and violet may appear to advance or recede, depending on the colors used with them. So some interior designers consider them neutrals that can complement any color scheme.
Can you mix warm and cool colors? Absolutely. In fact, a warm color scheme often benefits from at least a hint of a cool color to create balance. And a cool scheme may need a burst of warmth to liven it up.
The combination of warm and cool colors generally intensifies the relative temperature of each. One room featuring a predominantly warm color next to a predominantly cool room can make the rooms seem more intensely warm or cool. Consider this effect when selecting your flooring or carpet.