Question

what colour difference would you observe on burning a candle and a magnesium ribbon?

Answer 1

if you are talking about color difference only then a candle when burns produces a yellow color flame whereas magnesium ribbon produces a dazzling bright flame

Answer 2

a dazzling bright light could be seen when magnesium is burnt in air but in case of a candle its not much brighter than the magnesium and bright light of magnesium can affect our eyes.