What are the differences between the grades of maple syrup?
The grades reflect how much light can get through some standard quantity of maple.  The darker maple syrups tend to have a stronger maple flavor and tend to be harvested later in the season.  The collected sap needs to be concentrated and purified to make the syrup, which is traditionally done by boiling and skimming off impurities.

The USDA (United States Department of Agriculture) and the CFIA (Canadian Food Inspection Agency) have similar grades for maple syrups:



The CFIA standard requires measuring the grades using green light (560nm) light.