You mentioned Relay for Life ... and yet I don't see a "pink" ribbon, that would be their colour.
You might want to take a look at the different awareness ribbons as to what groups are represented by what you already have ... and decide which you want to use for your extra block?
http://en.wikipedia.org/wiki/List_of_awareness_ribbons
Sashing ... what about bordering each block with something that coordinates with it's ribbon, and then put them side-by-side?