You can change the color mode with the canvas tool.
This is convenient when you want to switch from color to monochrome illustration production such as manga.

Open the ①Tool Select window and select the ②Canvas tool.

Select ①Color Mode.

Select any color mode from ①Color Mode.
This time, select ②Gray Scale.

The color mode of the canvas has changed to Gray Scale.

When Black & White is selected, it changes in this way.

We are done.