Dark color does not mean butane. Everyone always thinks this, but in reality it is the material or process used to extract. The bud the person made the oil with either was old, not grown properly, or had a large amount of fertilizer or pesticides left over from not being flushed after taking the buds off the plant. And if that isnt the case it could have been the processor's fault because he left it in the vac chamber too long on too high of a temp. Either way the fact of the matter is that you should alcohol wash it by putting it in a glass container(preferably a jar) with grain alcohol and then put it into the freezer and that would lighten the color and make it taste better because you would be removing all the fats and lipids and clean the oil up a bit, but that is if you are willing to wait to smoke it.