You have a solid team. Your offense is balanced to remain competitive in all batting categories and I like your choices for closers. I was about to say that your pitching might be lacking some but then I noticed that I didn't see Smoltz. You starters are good. Overall, you have a good team, especially considering this is your first year playing. You didn't draft too young, as some owners would draft rookies way too early and expect them to contribute this year. Betancourt, if he holds on the closer role, should be serviceable. One Yahoo fantasy expert, Andy Behrens, wrote this: "If you added 30-something saves to last season's stats, Betancourt would have been an elite closer, similar in value to Papelbon, Nathan and Putz. That might be the best reason to pick him up." That might be best-case scenario though. I would put him as a middle-tier closer.
In yahoo, when you go to the "My Team" page, it shows a lineup, C, 1B, 2B, etc., that you could place your players (if they are able to play that position). So for example, Konerko, a 1B, can only be placed in the 1B slot, UTIL slot, or the bench (BN). If a player is on the bench slots, you don't get the stats he produced (if a player is slumping, it might be better to have him on the bench until he starts hitting). Same thing for pitching. On the day of games, starters who are pitching that day will usually have a " ^ " in front of the Opp column. Relievers (RP) don't have that, usually you just leave them in the lineup. For the "There are light colored backgrounds on some players and dark colored on others," I think you are talking about in the lineups and in the "Players" section, and anywhere actually. It is nothing. I think it is a way to help the eyes see as they go across the page.
One strategy for Head-to-Head leagues is streaming pitchers. Look / read around for more information as well as for other strategies or how to play Head-to-Head. Good luck in your season and I hope you enjoy playing fantasy baseball.