What other colors does he like?
I would want the quilt to be lighter/brighter than these walls.
So you could find varying lighter tones of the same green or add tans or taupes and cream.
Maybe add some rust, orange, brick red for the bright accents.
I'm learning that I need more lights and brights in mine. I love the deep, rich colors but without the lighter, brighter to go with them, they don't have good contrast and end up almost depressing. (Or I put only brights and need sunglasses. Lol. !)