Answer: For red color firework we will use combination of strontium carbonate with lithium carbonate and for purple color we will use combination of strontium salts with copper salts.
Step-by-step explanation:
There are various metallic salts which on performing flame test imparts characteristic color to the flame and this color is due to presence metal ions.
Color seen during the fireworks are mainly due to the presence of the metal ions present in the material from which the firework is made.
for example : strontium carbonate on flame test imparts bright red color to the flame where as barium chloride imparts green color to the flame.
The combinations of compounds are:
For red color firework we will use the combination of strontium carbonate with lithium carbonate because combination strontium and lithium ions both imparts red color to the flame.
For purple color we will use the combination of strontium salts with copper salts because combination of strontium and copper ions imparts purple color to the flame.