Is it possible to colour a range of cells based upon a check box ie if
it is checked, a particular range is green or if its unchecked the
range is red ?

Here's one way.

After adding a check-box using the Forms tool bar, right-click on the tool
check-box and use
Format control Control

There, select the "Unchecked" button, and in the "Cell link" indicate a
helper cell in some out-of-the-way place. That cell will contain logical
TRUE or FALSE depending on whether or not the check-box is checked. Then
select the "range of cells" and use
Format Conditional formatting
With formulas referring to the helper cell.