🚀 go-pugleaf

I have a question
I have been working with circuits for quiet some time now. I have noticed
a phenomenon of difference in color of the sparks at the switches depending on
the type of current used.
for the DC the sparks are brilliant white
for the Ac the sparks are blue with touch of yellow
 please note that I did not have a capacitor in the circuit(honest)
and this seems to hold true for comparable voltages
I have been using this phenomenon of observing the sparks and figuring
what type of current the circuit carries when I dont have a meter handy
(not a good practice, I have fused many a I.C by not being carefull , but beats
the method of working blindly) 
also note it is possible to figure if the circuit has both the components ( Ac
and DC)
 If some kind soul could explain the basis of this phenomenon I would
be very much obliged.
 dose the key lie in the fact that a lamp on dc gives white (?) light compared 
to lamp run on ac pale yellow ?