Grease Pencil: how to adjust color of "canvas" drawing plane guide?

There’s a checkboard/grid guide to the drawing plane called the ‘canvas’. I’d like to change it’s color, but can’t determine which parameter it is in the 3dViewport Themes panel.

Anybody know?


Click on the Grease Pencil Object / Object Data Properties on the right (the squigly green line) / Canvas / Color