Good print quality, but colors are not opaque

The quality is good, and the ink colors are rich, but I feel that there should should be a base white layer to ensure that colors remain true when the sticker is placed over non white backgrounds. On my aluminum MacBook for instance, bright yellow is darkened and becomes desaturated. It would also be useful if the backing paper was black or slightly patterned to make it more obvious that stickers are clear before they're peeled off.