A spectral colour is a colour corresponding with a single wavelength of visible light, or with a narrow band of adjacent wavelengths.
The human eye, and so human perception, is tuned to the visible spectrum and so to spectral colours between red and violet. However, because of the way the eye works, we can see many other colours which are produced by mixing colours from different areas of the spectrum. A particularly useful range of colours is produced by mixing red, green and blue light.
RGB colour is an entirely different approach to producing and managing colour.
RGB colour is an additive colour model in which red, green and blue light is combined in various proportions to reproduce a wide range of other colours. The name of the model comes from the initials of the three additive primary colours, red, green, and blue.
Except for the three primary colours, RGB colours are not spectral colours because they are produced by combining colours from different areas of the visible spectrum.
RGB colour provides the basis for a wide range of technologies used to reproduce digital colour.
RGB colour provides the basis for reproducing colour in ways that are well aligned with human perception.
When an observer has separate controls allowing them to adjust the intensity of overlapping red, green and blue coloured lights they are able to create a match for a very extensive range of colours.
When looking at any modern display device such as a computer screen, mobile phone or projector we are looking at RGB colour.
Magenta is an RGB colour for which there is no equivalent spectral colour.