The checkerboard grid identifies
transparency in a layer. You can change the appearance of this grid;
however, do not change it to solid white because you’ll eliminate
the visual distinction between opaque (white) and transparent (checkerboard).
Choose Photoshop Elements >
Preferences > Transparency.
Choose a pattern size from the Grid Size menu.
Choose a pattern color from the Grid Colors menu. To
choose a custom color instead, click one of the two boxes below
the Grid Colors menu and select a color from the Color Picker.