Assume your dates are in column A, starting with cell A2. Highlight
all the cells, with A2 the active cell. Click on Format | Conditional
Formatting, and in the first box that pops up choose Formula Is rather
than Cell Value Is. In the next box put this formula:
=(WEEKDAY(A2,2)>5
Then click on the Format button, and click on Colour (to affect the
foreground colour) and choose the colour you want (eg red). You could
also click on Bold, and if you click on the Patterns tab this affects
the background colour - you might choose bright green. You need to
click OK twice to exit the dialogue boxes, and then any cells which
have weekend dates in the range you had selected will now appear red
on a bright green backgound.
Hope this helps.
Pete