how can i find out which color candle will burn fastest

I think it has more to do with the type of candle along with the wick (slow burning or not) and not the dye.

could it the white one somehow be in a colder position?
candles )of any colou burn much longer if they are kept in the freezer.

Different types and combinations of wax and fats will burn at different rates.
Candles can be made from tallow, parrafin wax and bees wax. there are probably more waxes that may be used that i dont know about

The best way would be light the wick.

Maybe they add some sort of combustible material to the colored ones, like gasoline. This would make them burn fast. MUCH faster.

I find that when candling eggs, the brown shelled ones are more quickly overdone.

I think it was Joe Nation that answered this on another thread.

I think yellow and pink color candles burn fast.