User blog comment:Lightning the Skrill/Skrill's Lightning Blast; White Fire?/@comment-25863920-20150327201938

The definition of conductive is any material with less than 10^-2 / cm of special resistance and unconductive is more than 10^5/cm. As the current increases, this number of resistance gets lower in the equotation and as a result , current can pass many objects that were considered unconductive. At some point, this can pass through air , what tesla coils do. The color of the skrills fire can help determine the voltage. If the voltage is different so is the color which might explain the question. The whole thing that skrills can hold electricity is their powerful capacitance (e.g the human body has nanofarads of capacitance ) @ high voltage. If the capacitance of the skrill is variable, again , so is the color. Higher capacitance would allow more voltage at the cost of higher Frequency (e.g city electricity has 50-60 hz). If the skrills capacitor is his body, so the capacitance is changed with the size , and the voltage changes with his size and as a result , the lightning color changes with his size , maybe the skrill in Book of dragons short is different than the one in the series.