change background color

I have a worksheet, using column b9:f550 with the cells having a background color of blue.  Col B is empty of data.  whenever I put a S or P in column B, ( b9 example, I want the background color to change in b9, c9, d9, e9, f9 to white.   is there a way that this will automatically change to white whenever I add a S or P in the B col?