Normally oxygen is concerned, but hydrogen burning in chlorine also creates a flame, developing hydrogen chloride (HCl). Other doable mixtures creating flames, amongst quite a few, are fluorine and hydrogen, and hydrazine and nitrogen tetroxide. Hydrogen and hydrazine/UDMH flames are equally pale blue, although burning boron and its compounds, http://codyggged.canariblogs.com/getting-my-fire-damage-to-work-6874050