I am trying to change the colour of a cell using the "If Function" i.e. If value of the cell is greater than 20, change colour of cell to green, else colour to be red.

Hi
Try using Format>Conditional Formating.
Thanks for the reply but i didn't really understand it. Could you please give me an example of the function that would relate to my earlier question. Thanks
Hi
Select all the cells you want coloured then select Format>Cells>Pattern Tab and select your red color, to color all the cells.
Select them all again and select Format>Conditional Format and select or enter these values.| Cell Format is | between | 20 | 1000 |
then select your Format>Patterns from the same dialog and choose you green color.
Change the 1000 to your own upper limit.
