I like this color combo (sea green over navy blue) over dark denim, sweater needs the heathered knit, not solid if wearing a non traditional color. J Crew style, sea green cotton sweatshirt worn over blue checked shirt with denim.
The Ultimate Men's Flannel Collection: made of soft, sturdy, midweight flannel. Two front pockets with button flaps. This is not your pajama party flannel. (Or 90's grunge.) This is the flannel shirt he wants to wear (and you want to see him in).