Apparently not too many people here understand about emission spectra! Hint: The color you see is based on the energy in the system....different energies...different emission spectra....some of them you can see, some of them you can't.....heat and pressure are "energy"! Second hint: The "higher energy" emission of strontium is in the near-Ultra-Violet, which isn't visible to the naked eye....the "lower energy" emission is red....the color shifts or "lights-up" when the over-all energy in the chemical system drops....not because it hasn't been "burning" the entire time!

Didn't ANYBODY take chemistry in high school?