Use Conditional Formatting.
Cell Value "less than" 0 and set format to red (font or fill), then add
a second condition
Cell Value "greater than" 0 and set the format to green.


"Rob" wrote:

I want a cell to be coloured red if the result of a simple calculation is
negative, and coloured green if the result is positive. Can anyone tell me
how to do this?
--
Thanks for your help

Rob