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

The colours in fireworks come from metal salts that emit characteristic wavelengths when heated; strontium salts produce red hues and barium salts produce green hues. Official reporting and technical summaries list strontium salts (nitrates, carbonates, sulphates) as the source of red colour and barium salts (nitrates, chlorides) as the source of green colour in firecrackers and display shells [1]. Pyrotechnic guides and industry discussions likewise identify strontium compounds (e.g., strontium carbonate/nitrate) for red and barium compounds (e.g., barium nitrate/chloride) for green effects. Therefore, the salts of strontium and barium (option 3) are the correct choice.

Sources

1. [1] https://www.thehindu.com/news/national/after-sc-order-focus-on-chemicals-in-firecrackers/article62048017.ece