Pink- Lithium Salts or Lithium Nitrate (NO3), Yellow- Sodium Salts or Sodium Nitrate (NO3)
Explanation:
These chemicals (Sr, Ba, Cu, Ca, Na, Mg) are used because they create the colors for the firework. As you can see, the chemicals Nitrogen (N) and Oxygen (O) are combined with the color chemicals to make them combust.
The chart below explains the colorants used in firework creations:
Color= Compound
Red= strontium salts, lithium salts
lithium carbonate, Li2CO3 = red
strontium carbonate, SrCO3 = bright red
Orange= calcium salts
calcium chloride, CaCl2
calcium sulfate, CaSO4·xH2O, where x = 0,2,3,5
Gold= incandescence of iron (with carbon), charcoal, or lampblack
Yellow= sodium compounds
sodium nitrate, NaNO3
cryolite, Na3AlF6
Electric White= white-hot metal, such as magnesium or aluminum
barium oxide, BaO
Green= barium compounds + chlorine producer
barium chloride, BaCl+ = bright green
Blue= copper compounds + chlorine producer
copper acetoarsenite (Paris Green), Cu3As2O3Cu(C2H3O2)2 = blue
copper (I) chloride, CuCl = turquoise blue
Purple= mixture of strontium (red) and copper (blue) compounds
Silver= burning aluminum, titanium, or magnesium powder or flakes
I hope this answers the question you have! If not, I apologize.