This does not mean that your vape oil cartridge misbehaves as well as requires to be disposed of. When you expose your vape juice or e-liquid to extreme sunshine or warmth, it can cause it to alter from a light clear color to a much darker coffee color. This is due to the fact that the sugar and also the pure nicotine in your vape fluid will slowly start to break down as well as transform your e-liquid from a clear color to a darker caramel shade. vape juice changes colour when revealed to light and oxygen. This is triggered by chemical reactions that create some break down of constituents.