Change grid color?

How do I change the color of the grid lines (and the thickness!) that I’m putting onto my photos?

Choose View -> Guides and Grids -> Grid Settings. Color is then the second choice in the appearing panel. There is no option for thickness there… so I assume you cannot change it.

There’s also the Grid filter, which will let you change the width and color of the Grid. You can alter those settings from the Filters panel.