need a refernce for why dark candles burn faster than light colored candles?

Answer 1

It has to do with the size of the wick more than it does color. The wider the wick, the faster it pulls up molten wax to burn off.

The best way to test this is to take two candles that are identical except for color. Buy the same brand, size, everything. You'll see that they burn the same, or the darker candle may even burn slower (because of the color additives which make burning less efficient)