White is a very suitable color to accent gray or for the trim on a gray home. Most shades of white are suitable for gray-colored home exteriors from bright, pure whites such as super fine white to off-white colors such as biscuit or eggshell. Take a paint chip of your original gray with you to the store to match it with a cool- or warm-toned white, appropriately.
Although some blues are too light to use as an accent color for gray, muted and subdued shades of blue are suitable and can add a touch of sophisticated color while retaining the neutral feel of the home's exterior. Slate blue works particularly well with many grays.
Fawn is a warm, rich and vibrant muted brown that resembles baked clay. This color works best with light grays, and may not be suitable for darker shades such as charcoal gray or gunmetal gray.
Green gives a friendly, organic feeling to a gray house. Both darker greens, such as forest green, and lighter ones, such as sage, are suitable with most shades of gray exterior paint.
Another paint that works both in vibrant and subdued shades is red. This color can sharply define the trim of a home or quietly complement a gray exterior, depending on the vibrancy of the shade chosen. A red entry door on a gray house is a timeless, classic treatment.
Dark, deep and unmistakable, black will sharply define any part of the exterior it's applied to. Although this color is very compatible with gray, it is usually confined to use on shutters or the entry door in a color scheme that also includes white trim.
Both mauve and lighter, muted shades of purple are compatible with the colors of a gray home, either as trim or as an accent color in a larger color scheme. Lilac, for example, can brighten the overall appearance of a home. More colorful and vibrant shades of deep purple may be too loud.