FWIW, I use an Eagle Creek ORV Trunk 30 and a #5 Duffle from Bad Bags. I carry clothes, hard hat, steel toes, harness, respirator, and other items in them and have found them adequate so far. The Eagle Creek is obviously 30" and the Duffle is 28".

As far as color unless you plan on flying with clients I wouldn't overly worry about professional color selection, but just my opinion. My bags are black and red.