In the 19th century, it was common practice to add blue dye, such as Prussian blue or ultramarine, to sugar to improve its appearance and make it appear whiter. This practice was part of the widespread use of artificial colors in food, many of which were toxic. The use of blue dye in sugar was eventually regulated, but it remained a problem for decades.

The adulteration of sugar with blue dye was a subject of satire and social commentary, with poets and writers mocking the practice of 'improving' food with chemicals. The theme of artificial colors hiding decay was a powerful metaphor for Victorian society's obsession with appearances. This theme appears in the works of writers like Oscar Wilde and the Aesthetic movement.