And you can NOT get magenta with just any old red or blue shade, of which there are many! You need a red that has pink undertones. You'll NEVER get it with a red that has an orange undertone.
Wiki: purple
In optics, violet is a spectral color; it refers to the color of any different single wavelength of light on the short wavelength end of the visible spectrum, between approximately 380 and 450 nanometers,[58] whereas purple is the color of various combinations of red, blue, and violet light,