Specifying cell fill patterns and colors

In Design mode, right-click the cell or cells to format and select Format Cells.

You can choose the primary color for the background of a cell.
Note: On the Pattern tab you can apply a background color to one or more cells. But you cannot apply a background color to all spreadsheet cells. To apply a background color to all spreadsheet cells, or to insert a background image, select Format > Background.

When you set a fill pattern to a spreadsheet cell, it is displayed as white on the web.