Conditional formatting based on neighboring cell

Hi.  I'm looking for some help figuring out what the best way to go about this is.  I've got a sign-in sheet to keep track of guests that are in a building.  One column is a list of the guests names, and in the cell to the left there is a drop-down menu containing a list of the hosts.  The drop down menu is getting it's information from a different sheet that has a list of the hosts' names.  Next to the column containing the list of the hosts' names, there is a column that states whether they're allowed to sign in guests at the moment - Yes or No.

What I need to do is change the color of the cell on the first sheet based on whether the host is allowed to have guests or not.  Any ideas?