What I love about shirts and shirtings is that they are and should be an easy source of inspiration. In other words, one should feel an extra degree of freedom with which to pick and choose novel patterns and distinctive colors. As a rule I think it's fair to say that men should be experimenting more with colors and patterns in shirts than with suits or jackets.
If you tend to be a "classic" dresser, give this a shot. Experiment with your next shirt or shirting with something sharper, more vibrant than your usual safe choice. In particular, I especially like the new plaids in the upcoming spring/summer delivery of Hamilton Shirts 1883 (see below).
These are not just casual shirts worn with khakis, chinos or jeans. Actually, I would wear the first two plaids with a seersucker or solid cotton suit and pair them with a dark brown tie and black (or navy blue) tie, respectively. In particular, I think solid cotton or silk knit ties work very well here.