Use the darker shade in the area you want to de-emphasize. The lighter shade can be used to balance the larger areas. An important factor to consider about color is to select colors that are becoming to you. When selecting fabric consider texture, surface design as well as its hand or weight. This is important when selecting appropriate clothing to look pounds thinner.
Texture is surface interest.
The texture determines how the fabric feels, looks, and moves when it is worn. It may be seen, felt, and even heard at times. Textures have weight, size, bulk and light absorbing or reflecting properties. To appear pounds thinner look for fabrics that are medium to lightweight which are crisp, but not stiff. Very stiff fabrics appear to add weight to the body.