K= 769 nm (deep deep red) Rb = 780 nm and 794 nm (still deep red) Cs = 852 and 894 nm (near infrared, not visible to human eye) Now you are right, K flame appears violet to us and Cs is indeed blue. As stated above, potassium salts in Bunsen flame also show. K = 404 nm (deep violet) Now violet and red wavelengths appear

Purpleflames, on the other hand, are usually not as hot as blue flames. Purple flames can be produced by the presence of certain chemicals in the flame, such as copper or mercury. These chemicals can absorb light in the blue and green part of the spectrum and emit it as purple light, which gives the flame a purple color.

deep purple in flames