Macarons using darker-colored frosting—such as deep reds, blacks, blues, or purples—may leave temporary stains on the tongue, teeth, and hands due to the high concentration of food coloring required. Additionally, the taste may be slightly bitter or chemical-like, especially when large amounts of dark gel food coloring are used. This is a common characteristic of dark-colored frostings and is not harmful, but it may affect overall flavor and eating experience.