Auto fill coloring of a cell with a specific letter

Hello
I am working on a spreadsheet here at work and I have run into a problem we have not been able to solve. We have a spreadsheet built using the days of the month and all our employees. We are tracking field days(F), days off(O), etc.
I am using COUNTIF to sum up the row for each employee.
The letters we are using in the cells are F,O,S and T. I would like to be able to assign a fill color to each cell depending on the Letter that is entered.
Thanks in advance for any help you can supply.
Bill McRae

Thanks for replying oldchippy. I will try that today.