I am trying to colour a cell based on another cell's value.

I have a table with 4 status titles e.g. green, amber, red and blue. If the
value under the 'green' cell is greater than the values for 'amber', 'red' or
'blue', I want the target cell to be coloured green.

Likewise, if the value under the 'amber' cell is greater than the values for
'green', 'red' or 'blue', I want the target cell to be coloured amber.

So far I have tried conditional formatting but no joy. Any ideas gratefully
received.