Salts of which of the following elements provide colours to fireworks?

1. Fireworks produce various colours through the incandescence of metal-containing salts when heated. 2. Different metal ions emit light at specific wavelengths when excited, resulting in distinct colours. 3. Strontium salts (like strontium carbonate) are commonly used to produce bright red colours. 4. Barium salts (like barium chloride or nitrate) are used to produce green colours. 5. Other examples include sodium for yellow/orange, copper for blue, calcium for orange, etc. 6. Zinc and sulphur are used in some firework compositions but not primarily for colour. Potassium (e.g., potassium nitrate) is an oxidizer. Mercury is toxic and generally not used. Chromium and nickel are not typically used for colours in common fireworks. Therefore, salts of Strontium and barium are key elements providing colours to fireworks (red and green, respectively).