In a Board, ideas are displayed on a white background. However, you can enable or disable the display of a grid.
1 - Access display options
Click on the cogwheel at the bottom right of your Board, or press the shortcut SHIFT+G.
2 - Select "Show grid" option
3 - The grid is displayed
To hide the grid, simply reverse the process.
To find out more about how to set up your Board, see the articles available on this link.