It is really hard to produce quilts that are non-gendered, for males of all ages. And I really balk myself at the whole idea of "boy quilts/girl quilts".
This is where the colour wheel is your friend...try using the intermediate colours ie. red-orange, purples, yellow-greens. Essex linens also play well for non-gender quilts.
For older males, the Japanese dobby cloth fabrics come in textured, muted tones that make elegant, non-gendered quilts.