Shopping is not as simple as you may think! Much has to be done for the producers before putting the products on the shelf. Color, for example, changes a lot according to what the producers are trying to sell. Health foods are packed in greens, yellows or browns because we think of these as healthy colors. When some kind of medicine was brought out recently, researchers found that the color of the package  caused the shoppers to lose interest because they made the product look ineffective . At last, it came on the market in dark blue and white--blue because we think of it as safe, and white as calm. The size of a package can also attract  a shopper, although quite often a bottle doesn't hold as much as it seems to. It is said that the better-known companies spend about 40 percent of the cost of the product itself on packaging! The most successful producers know that it's not enough to have a good product. The head of Pears Soap, who for 25 years has used pretty little girls to sell their goods, came to the conclusion: "Any fool can make soap, but it takes a talent to sell it." Health foods are usually packed in colors Except   _  .
green black yellow brown