To change the background color of a cell, or range of cells, first select the cell, or range, and then do the following:
Select the Cells command from the Format menu (or right-click and select Format Cells).
Select the Color tab in the "Format" dialog box. The "Color" dialog is displayed.
Select a color from the Basic colors box.
Click OK to apply the color to the selected cell or range.
In addition to the basic colors you can "design" your own custom color:
Enter the "Color" dialog box as above.
Click on the Define Custom Colors button. This expands the right side of the box to display a color chart.
Use your mouse to pick a color from the chart. Once you’ve done this you can refine your choice in the color bar at the side of the chart. The result will be previewed in the Color/Solid box below.
Click on Add Custom Color to add the color to the Custom colors section at the left of the box.
Click on OK to apply the custom color.
In future you can enter the box and choose any of the custom colors you have designed and saved.
Note that there are boxes for Hue, Saturation and Luminosity, as well as Red, Green and Blue. The values in these boxes change with the color selections you make. You can type in values directly that will find and display the matching color.
Also, note that a background color can be applied to the whole of a worksheet in a spreadsheet. To do this follow these steps:
Select Sheets from the Format menu.
Select Background from the drop-down list.
The "Color" dialog box is displayed.
Follow the same procedures as above.
The applied color will affect all of the current worksheet, rather than just selected cells.