Every color has shades within its colorway. < p> Even a single pigment color DOES have different qualities/shades within in it. Re watercolor...the shade depends on how much or how little water is added to the color, as well as if you use a dry ( none wet paper) or wet ( a dampened paper ) on which to paint.
By adding more water and/or painting "wet", you are able to paint a violet hue, by using a purple ( and there are many different shades, as well as mixes in the purple range ) color and a LOT of water.
“Inside a color band are many different shades and violet IS a shade of PURPLE!”
Violet has its own part of the visible spectrum. Purple is a not part of that spectrum. It also has to have frequencies of red mixed in.
See #27