Yep. What CCC said. I vape flavorless
juice, which is crystal clear when it goes in the carto, but when a bit leaks out onto the connector it's sort of tan, and becomes darker (eventually sort of a cola brown color) as I use the carto. Nic
juice will also turn progressively darker if you leave it out in the light. After I mix up a batch of
juice, I end up with two 120ml bottles that I leave in the fridge and a 60ml bottle that I leave out on the kitchen counter ready for use (i slowly feed this into a small 10ml bottle that I carry with me). After about a week, the bottle that's been sitting out has turned sort of a light pinkish tan color, while the stuff in the fridge is still totally clear. The juice that's left out still vapes, tastes, and smells the same, so I don't think it hurts anything, it just gets darker colored.