Hi Tiffany,
Conditional processing is applied "top to bottom" in that it will display whatever criteria first matches the data for a particular report row, so in your case, you could add a first rule that checks for Last Login Date that is NOT blank and formats those in a certain way (e.g. green background), and then add a second rule that checks for Entry Date less than 6 months that sets the background yellow, and (optionally, but I believe consistent and of value) add a third rule that checks for Entry Date not blank (effectively, "always true, if you get this far") with a red background, calling out those users set up over 6 months ago but who have still never logged in (suggesting their license could be recouped and repurposed).
Regards,
Doug