Well zinc makes a bright blue electrical spark, and its salts color non-luminous flames blue, so it should burn blue. Or white if it got hot enough to incandesce like aluminum and magnesium do, but it takes a lot of heat to ignite aluminum or magnesium (and the result would look like one of those sparkler fireworks things).
OK Elysian now Iām curious 
- what color and how intense was the flame?