Hey with three colors I love all of the suggestions, rail fence, jacob's ladder and irish chain.... and the pinwheel is another good idea... log cabin is one of my favorite patterns... you could tie the theme with his graduation such as "ladder to success" using jacob's ladder or "reach for the stars" make sawtooth stars with all of his favorite colors..
log cabin can be " home is where you come from to reach your goals" or always come home to find love and support..
Just throwing out ideas... he will love the quilt because it is made with love..
hugs
quiltinmama