I gather Ahlusion makes some of its own flavor extracts. Those would be in the really clear flavors. Deej said that a lot of the flavors come with coloring in them (he wished they didn't.) Those are the ones that start out caramel-colored. And there are a few flavors that are quite dark when the juice vendor receives them. Those are the coil killers but some of them (Gingerbread) are worth it.
Once the liquid is mixed, it darkens as the nicotine ages and oxidizes. So either ECBlends is getting their flavors from a source that uses a lot of food coloring or they are buying their nicotine in large quantities and not protecting it from oxidization before it is used -- or a combination of the two.
So when the juice in your tank turns dark is that due to the nic oxidizing or just discoloration from the heat of the atomizer?