Don’t over-blend your background so that it’s smooth and flat. Objects look more three-dimensional with a blurry or choppy backdrop, even if the variation in value or color is slight. Your subject will look like a cut-out (like a person in front of a green screen) without a little variation behind it. You can mix a few similar colors to achieve the mottling of this depth technique; just don’t blend them on canvas to the point where they disappear into each other.