How to draw the starry sky with gouache pigment? . Can draw. Help!

As can be seen from the chromaticity bars in the above figure, colors can be obtained from cyan and blue.

Gouache can be ultramarine and blue.

You can add a little coal black if you need to deepen it.

Try the proportions yourself.

The component of 1 is squeezed first: 1.

Green plus blue, blue plus green.