How can I set up a plain frame edge instead of bevel in PiP?

I have CS5.5.  I am trying to display 4 different pictures on the screen at the same time.  I would like to change out the pictures to music.   I tried to use PiP and found that the only choice of edges was a bevel type.   I need to know how to make the edges flat so it appears as a square(frame).  Prefer to have each edge a different color.  But not necessary if I can have them something other than black.    

Thanks in advance,

Duane