White is a clean color that makes a house look crisp and neat. Painting the trim of your gray home white is a classic way to accent the lines of your house and set off the darker gray color. Black is another traditional color used to accent your home. Shutters and other added-on architectural features are often painted black.
Pair your gray with other neutral colors besides white and black if you want a less traditional looking house. Substitute a light fawn color (which is a gray-brown) for the white trim, and use a steel-blue or slate green for the shutters. Both of these are cool colors found in nature that will give your home a fresh, organic look and will complement gray siding.
Pairing warm colors with cool gray may seem contradictory, but warm colors can actually cozy up an overly-cool house. Too much gray, especially on a large home, can inadvertently make that home feel dreary. Try warming up the gray exterior of your home with a rich burgundy or maroon color or a very soft, pale yellow.
Create a cohesive look by sticking with one family of colors on your house exterior. Use other grays to complement the primary gray color in your house. Just ensure that you choose grays in the same hue as the gray siding. For example, if the siding color is a dusty blue-gray, paint the trim in a darker charcoal gray, but see that it is also tinted blue. Instead of white, use a creamy, pearly gray on accent areas, such as around the windows and on porch railings.