Most people are aware that food with bright or unnatural colors , such as the green ketchup mentioned , contains food coloring . Far fewer people know that `` natural '' foods such as oranges and salmon may also be dyed to hide natural variations in color . While most consumers are aware that food with bright or unnatural colors ( such as the green ketchup mentioned above , or children 's cereals such as Froot Loops ) likely contain food coloring , far fewer people know that seemingly `` natural '' foods such as oranges and salmon are sometimes also dyed to mask natural variations in color .