Cobalt Violet , cobalt phosphate, was discovered just before Manganese Violet. Cobalt Violet is a pure hue that cannot be mixed from other colors. Cool in its masstone, Cobalt Violet greys down considerably when mixed with white. The modern Dioxazine Purple has the strongest tinting strength of all pigments. A cold color, Dioxazine Purple is completely transparent and useful as a high key tint.
Some painters never buy violet or purple.
They mix it using Alizarin Crimson and Ultramarine Blue. While a decent color, the purple mixed using Alizarin Crimson is not lightfast. Within 100 years that mixture will not be purple, it will be blue. Mixing Ultramarine Blue with lightfast and transparent Quinacridone Red or Magenta will make a permanent purple of much higher chroma.