Olive green is a slightly yellowish green, usually characterized by a bit of a neutral shade. Neutral shades, those in the range of gray or browns, are a mix of all colors. Since olive green is somewhat tempered by its neutral component, it is easier to pair with other colors than brighter shades of green. Whether you are looking for a match for a room, a painting or for a hobby project, you have many options.
Yellow and Yellow-Green
Yellow is next to green on the color wheel, and goes with it very well. A bright yellow such as canary yellow will be a lively counterpart. Pastel yellow will work, too, letting the darker olive green take precedence. Gold is another option to consider, especially a metallic gold or bronze color. Yellow-greens also are options, with the brighter versions adding verve and snap.
Earth tones provide a solid pairing for olive green. They are not so colorful in themselves, but would give a solid base from which the olive green would stand out. Classic lighter colors such as taupe or tan are in this family. You could also use deeper earth tones like umber for contrast.
Red is the complement of green. As such, it will set up a dynamic contrast for the olive green. Vermilion, a brilliant red, would make a rich companion. Jewel colors such as garnet or ruby could also be successfully employed. For a softer red where the olive green stands out more, a fall color like russet will do the job.