Query on Xuanzong's ink

Xuanzong ink has four color grades, namely ink, medium thick ink, thick ink and extra thick ink. As far as black ink is concerned, it is also subdivided into different varieties. In order to adapt to the pursuit of purple jade luster by ink color and advocate the requirement that "ink color is superior to purple light", multiple levels of color scales and hues are subdivided in the same variety of ink of a certain brand. On the basis of purple ink color, there are three kinds of colors: purple, cyan and tea.