What is the difference in Maple syrup colours?
Answer provided by Sarah Cosman of Cosman and Webb Maple Syrup. 
The only reason a syrup is dark is because of the extra bacteria in the sap late in the season. There is no extra nutritional value to darker syrup, all syrup has the same nutrient content (another question we are often asked – mostly from people wanting to do a cleanse).
In the beginning of a season, typically staring in mid-February, the sap from the trees comes in very clear. This sap makes very light syrup without a lot of colour or maple flavour. Not much of this grade of syrup is made, and it’s highly coveted in Quebec (not a lot of farmers will share this syrup) – at least where we are in the townships :) Golden, Delicate Taste is the name of this grade.
Mid-season brings the best maple syrup, in our opinion. You get the best of both worlds – a light and delicate syrup with many flavour nuances but without any bitter, acrid, or chocolate flavours you might get with a dark syrup. The maple flavour is prominent but not sickeningly sweet. Amber, Rich Taste is the name of this grade and this is what we bottle.
Sap from the end of the season, usually starting in April when the weather starts to warm, starts to come in stringy and milky. This is due to the extra bacteria in the sap which the trees need to open their buds. This bacteria will quicken the caramelization time of the sugars in the sap, and because we have to boil the sap until it’s 66.6% sugar, the long boiling time creates the darker syrup. The darker syrup can often be bitter and acrid in the back of your throat, but it will have a stronger maple flavour with caramel notes which some people find desirable. Dark, Robust Taste is the name of this grade.
Syrup farmers have to be careful when making dark syrup as the flavours can change quickly when boiling. When the syrup starts to taste chocolatey, like a tootsie roll, this is called buddy syrup which is classified as commercial grade. We’re not allowed to bottle and sell buddy syrup (FPAQ regulations) but we can sell it as fertilizer or as an animal feed supplement.