What wall color add to wall if furniture is dark brown and pillow accents are green?

Depends upon where you live... if you live in a sunny climate (Florida, S. Cal), you could use any number of vibrant colors (coral, orange, yellow, red...). If you live in a northern area (where daylight may be muted and hours of light may be short) you would be better off to stick to a muted palate and use shades that are somewhat 'pastel' or cream based - mint green, sky blue, pale peach or pink, buttery yellow. The color itself is not as much the question as the tone of the color!