What scale is used to label the color of sugar?

The International Commission for Uniform Methods of Sugar Analysis Ltd. (ICUMSA) grades sugar from a range of 0-6.

0 = maximum whiteness

6 = highly colored low-grade white sugar

In its purest state, sugar is made up of colorless, transparent crystals. Freshly squeezed from cane or sugarbeet, the solution will show a blue and black hue in liquid form. Due to the impurities from the cane or beers, the lime solution is added to precipitate or eliminate them. When the sugar cools, depending on the extent of the additional purification and crystallization process it undergoes, it will take on a color form scaling between 0 and 6. The more it is purified and crystallized, the whiter it becomes.