The attire for the men in the wedding party, groom included, depends on the season, the personal taste of the bride and groom, if it is a formal or informal wedding, and the color story of the wedding itself.
Here are a few pointers:
Darker colors look slimming and quite elegant. That said, a beach wedding does look fantastic in white or off white.
Go with the flow of the wedding, if you are an informal type that is celebrating your wedding with a big backyard cookout, dress accordingly. You will be much more at ease and have fun if you are comfortable.
If the groomsmen and groom are identically dressed, choose something to set the groom apart, perhaps a different boutonniere that includes a flower that is in the bridal bouquet, a slightly different tie, or pocket square can do this easily.
If you are having a formal wedding that includes tuxedos, reserve about 3 months in advance. Measurements can be taken a few weeks beforehand, and be sure each man tries his on, including the shoes, a few days before. Trust me on this.
If you have out of town men in the wedding party, have them get their measurements done at a formalwear store in their area, then send them on to the shop you have reserved your tuxedos.
By all means show your individuality, especially if it is an informal wedding. Tuxedos don't work as well on a beach, but khakis and a nice linen shirt is perfect.