1、Aluminum-plastic flexible packages and aluminum-paper flexible packages: for these nontransparent packages, jus use colors as appropriate. 

　　2、Single PE packages: for these transparent packages, the color of the products the package is used for can be use as a complementary color, background color or decorative color (color of the transparent space), depending on the style of your design. 

　　3、The color of products in liquid form, like milk, soybean milk and juice, can be used as the background color of their flexible packages. 

　　4、The color of products in granule form, like coffee and monosodium glutamate, can be used as the background color of their flexible packages.

　　5、Some products in relatively larger pieces, like dried fruit and preserved fruit, are not recommended to be used as the background color of their flexible packages. For these packages, designers are recommended to leave a transparent space on the package, or use nontransparent color on the entire front side while just printing texts on the back side to make the products visible. 

　　6、There must be a sharp contrast between the bar code and the background color, and the product the package is used for cannot be used as the background of its package for fear that the barcode fails to be read by the barcode reader.

　　7、There must be a sharp contrast between the texts and the background color to ensure that the texts are readable.