Conditonal formating of rows

Hello,
I have a table in excel 2007, where column b has entries of names e.g. John, Devid, John, John, Gilbert, Devid etc. The same name may repeat more than once. I sort the table by names, and what I want is to color bunch of rows with say Devid name in cloun b with red color and next bunch of rows with next name with green color and so on so forth using only two colors.