There's nothing sacred about "primary" colors other than mixture of any two must not produce the third. "Additive" usually refers to emissive light such as the RGB red-green-blue from CRT picture tubes and their complements CMY cyan-magenta-blue respectively may also be emitted light. However they are considered "subtractive" when reflecting light such as by paint pigments. For example, Magenta loving vegetation reflects green and absorbs red and blue. Yet magenta is nonspectral, i.e. not in the rainbow.
Good luck with your color thesis---mine began in 1980