I make what I call "adolescent" quilts for PL. I often use greens just because I have a pretty deep stash of that color. But I use RWB or Blue with another color or a selection of what might be considered civil war shirting colors. I guess, I just avoid prints that are obviously pastel floral or baby. Let you heart lead you.
Last minute thought, consider animals or movie characters or sports. These could easily be used with solids or small prints to make good options for your group.