Combinations of strong and bright colors work well together in a boy's bedroom, as do bright or muted shades of beige and brown. Try kelly green with yellow accents for a sunny look. A warm latte shade painted on the walls gets a real pop from red furniture and framed artwork.
For an older boy, grey walls look great with black furnishings and accents—and consider adding a couple of touches of red or bright blue to catch the eye. An energetic boy might like a combination of red and orange, anchored by strong unpainted wood furniture.