Colour the cell using formula

Hello,

I am trying to prepare a worksheet which would help me to find out the payment status.

Column 1, Row 1 : Todays date

The below details on Row 2
Column 1 : credit period i.e. no of days
Column 2 : Invoice date
Column 3 : Due Date i.e. Credit period + Invoice date
Column 4 : Total Amount due
Column 5 : Amount recd
Column 6 : Balance Amount
Column 7 : Overdue by (Here I want your help) : To calculate the number of days overdue I am using the formula (=if(Column6>1,Row1-Column3,Column3-Column3). By using this formula I am getting the desired number of days but I want to add different colour to this cell to indicate the number of days as overdue (yellow), highly overdue (red) and not due (white),

Awaiting your reply

Thanks.